Printable or "print mini" paper minis are usually printed onto a piece of paper or sometimes thin cardstock that can be fed into a typical ink or laser jet printer - many paper mini users print onto paper first to make sure a mini looks good without having to waste more expensive cardstock, and then cut out and glue or otherwise affix the paper mini to the cardstock, which also adds extra strength, combining the cardstock and the paper.
Paper minis do not share a universal set of standards any more than regular minis, but do take many cues from them, and as such, most people do have a certain loose set of guidelines that govern how to create paper minis. I've gone through some good articles, posts and forums about this subject, and derived the following standards - naturally they should be altered to each individual's use or preferences. I'm omitting the smaller scales that are used for large armed forces conflicts, as you can have entire battleships be the same size as an RPG mini.
When dealing with miniatures, most of the time, the metric unit of the millimeter (mm) is used, with the different scales below, most of which I found here: http://theminiaturespage.com/ref/scales.html. A great debt of thanks to the author of this page for such a helpful and thorough listing of miniatures info!
1/107-100 or 15-16.1mm (0.55-0.59"): this scale is popular for "skirmish" tabletop wargames, meaning units or squads of roughly a dozen troops, rather than huge armies, as well as some mecha (fighting robots). This also appears to be the scale many historical gamers have settled on, from the larger 25mm.For the sake of simplicity and standardization, this work will assume the following as its default:
1/64 or 25mm (0.98"): the original and still basically default scale for tabletop role playing game miniatures; the odd thing about this scale is that it is a conditional scale, in that, depending on the company making the miniature, figure measurements may not be from bottom of foot to top of head, but bottom of foot to eye level. This was to allow for tall headgear, long weapons or things strapped on the back, etc., still keeping all figures within the same basic parameters up to a certain point. This essentially means that many or most 25mm minis are actually closer to 28mm (or at least have the potential leeway).
1/58 or 28mm (1.1"): "large 25mm" minis may be 28mm, as explained above, or a few non-standard minis may actually be made measuring 28mm from foot sole to eye level, making them more likely to be 30-32mm.
1/54 or 30mm (1.18"): this would be a "large 28mm" mini
1/x or 38mm (1.5"): a half size larger than 25mm, for special or deluxe gaming figures
1/40 or 40mm (1.57"): American Civil War figures - outdated, little used scale
1/35 or 46mm (1.8"): vehicle kits, deluxe or special figures for gaming
1/32 or 50.3mm (2"): I scale for model railroads, twice the size of a 25mm figure
1/29 or 54mm (2.2"): twice as big as a 28mm, for deluxe or special gaming figures
1/27 or 60mm (2.36"): double the 30mm figure, the largest practical tabletop figure
sole-eye = 25mm (0.98") actual measurements = 1600mm (5'3") scale measurements
So the first step in making a miniature is finding a suitable picture. You'll want a full body image of someone in a suitable stance or pose, making sure their width is about half their height or less (a little more or less is doable if you're used to resizing images in your favorite graphics editor). Obviously if you're making non-humanoids, like horses, you want their length (width) to be the highest value, and their height about half that. You'll also want the resolution to be 150 dpi or greater, 300 is optimum for print.
Finding Good Images
You can do searches in search engines for "full body" "pose" "stance" "action pose" or similar terms, and also look on Halloween costume and other similar sites, where you can usually download full body model images without much trouble. There are also actual model sites, as well as clothing catalogs that may have suitable images. Cosplay and convention images, television and movie stills and promos are good sources for full body images, as is Deviant Art and Elfwood, two large art sites where users may upload their own creations into their galleries to share with others. This is copyrighted and not "free art" except for personal use, and you should still drop the artist a line if you have gotten some good use of one of their images.
There are also public domain, royalty free and stock image sites that might have some suitable images, though many subtly mix free and commercial (paid) images and you'll find yourself constantly opening an image only to find you have to pay for a suitably large version. One positive though, is these sites often offer large images with their own watermark across it, which can fairly easily be remedied, either by free programs designed specifically to remove watermarks, or by a bit more lengthy manual editing. Remember, these images are only "free" for your own personal use unless they say otherwise (such as public domain).
Another resource which may yield some success is the Open Clip Art Library, where artists create and upload vector images (.svg) to their galleries to share with the world, similar to Deviant Art - the difference is, all these images really are free, completely and totally, for any purpose, including being modified and re-uploaded as new versions. Although there are legal differences, the OCAL is essentially a site to allows artists to create public domain images for others to use, and to allow them (and any other downloader) to use images from other OCAL artists for any endeavor (even commercial), including editing into a new image.
Visual Custom Hero Creators
Many may find online or downloadable visual hero creators useful for making minis. The downside is there are only a few poses, but the upside is, you can make custom heroes without having to know anything about art, except what you want your character to look like. A few sites: HeroMachine, Marvel Superhero Creator, and Fabrica De Herois.
Ideal Image Heights and Print Resolutions
If possible, however, since this is print, you want an image 1000 pixels in height or larger (600-800 will work but be a bit blurry, while 2000+ is excellent), with a color resolution of at least 150, to 300 dpi, the minimum and standard resolutions for print (72 is the default standard resolution for screen).
Depending on your tastes, you may actually be able to get by with low-detail "thumbnail" type images, since when you print things out at this size, a lot of detail is lost or "invisible" anyway, especially in the 600-1000 range. If your chosen image is closer to the 250-500 pixel height range, depending on resolution, it may still not turn out too bad, but there is a greater likelihood the final miniature will be pretty "fuzzy". One option is to "rotoscope" such images, using your graphics editor to resize the image to much larger dimensions and resolution, and tracing over the obvious "line" parts to make a simple cartoon version. This can be an involved process and is beyond the scope of this article, but you might look into it if you're interested.
Small and Large Races
Also note that, as noted at the preamble of this article, miniatures are assumed to be about 5'3" from sole of foot to eye level. Obviously this won't apply for small races like goblins and dwarves and such, so you could get by with smaller images of those (since they are smaller), so use common sense in your judgment - most images even for small folk still shouldn't be less than half the size of height-normative figures (in other words, they should be 3 feet or taller humanoids, and measure 12+ mm from sole to eye level. Obviously you invert this for larger-than-man-sized figures like orcs, trolls, etc. Probably 38-56 mm are suitable measurements for significantly large figures.
More on Height and Width
Remember, a mini's "smaller" dimension should be roughly half of their larger, so a 40mm tall mini needs to be around 20mm wide at most. These dimensions, however, refer to the full rectangle of the mini, not directly to the mini itself. Why? Because minis are measures from sole to eye level, not top of head, the 25mm is not their actual height. 4" is the average length of eye level to top of head, which by scale, works out to about 2 actual mm (each mm being 2.5" scale), for a total of 27 mm. Add to this helmets, hats, weapons held aloft, things strapped to the back, differing or isometric (angular, diagonal or partially top-down) stances and other details, and 28mm is the actual general height of a 25mm mini. Now some figures will be 27mm, but many will be saddled with additional headgear and such, to raise them above this, somewhere between 27 and 28. And guess what - that is still not the mini's final height.
Because these minis will be either "A-Frame" or "Inverted-T" structures, or even the unusual "Trifold", you add yet more empty space to the top of the mini for some "breathing room" or blank space, before the fold-point that connects the front to the back section. Usually one-half to a full head scale is sufficient for "overhead" (pardon the pun). Using our 25mm baseline, a head works out to be roughly 3.38mm, which is about 9.72" scale, which fairly dovetails with one artistic rule-of-thumb that says the human body is 7-8 heads tall (in this case 7), as well as real life measurements (the average actual head length is 9.5-10.25"). This means you need to add 1.5-3.5mm, an average of 2mm - which works out to a total of 30mm height (6'4" scale) for a 25mm mini, from sole to the fold-point.
Most people are roughly half as wide as they are tall, including their body or trunk, but also the general "zone" that their arms and legs occupy when not standing stock vertical, so a six foot tall person generally has a three foot wide "area width" - it doesn't mean their body is necessarily that wide (though some might come close), but that this space is commonly part of the path that their arms or legs occupy, either from being extended for holding items or arched with hands on hips, or feet set apart to improve balance or show readiness, a shield held partly to the side, etc. This works out to mean that a 30mm tall mini needs to be about 15mm wide, give or take, so when resizing or setting the "canvas size" for your mini, make sure that the image itself is smaller than 30mm tall and 15mm wide, but as close to those as you can get.
Finishing the Mini Front
So we'll assume you have a roughly appropriate sized figure in your favorite graphics editor - the most common being Adobe Photoshop (or CS), GIMP or other free program, such as Photofiltre. Make sure there is roughly half-a-head to a head (scale) of white space above the actual figure's head, and that the full canvas (the background of the image) is about half as wide as the height. Find the option to create a visible frame or border around your image. In Photoshop, Select > Select All > Edit > Stroke. In GIMP, Select > Select All then either Filters > Decor > Add Border or from Select All > Edit > Stroke just like Photoshop. This will put a nice border around your rectangle mini (probably make it 2-4 pixels).It is best to save your image (maybe as "mini01-front.jpg") once you have it at this point, as you have most of the truly important and involved steps completed.
Image and Canvas Resizing
Go into your graphics editor program, select Canvas Size, uncheck "constrain proportions" or whatever your application's term might be, sometimes represented by a lock or chain link, and resize only the height to double what it is now (from 30mm to 60mm) - make sure you set the "resize direction" (usually represented by a selection of arrows or crosshairs) to add the new space to the top of your image, so your image isn't plopped in the middle of blank space at top and bottom. Here is the final dimensions you should see in your graphics editor, for a finalized 25 (30)mm miniature:
Resolution: 300 pixels/inch (dpi)
Measure pxls in mm
Width 177 0.59 15
Height 709 2.363 60
Obviously you can round that to 180x710 (or 700) pixels or 0.60 x 2.4 inches.
Now, use your Magic Wand tool to select the blank area above your bordered image, and repeat the step for making a border or frame, so that you will have a mini broken into two equal sections by a border line (the fold-point) and the entire mini is also bordered (you may erase this if you choose).
Next, copy the figure image and paste it into the space above your figure (above the , and while it is still selected, go to your editor's selection for Edit and Transform and Flip Vertical (these will have different names or terms in different programs), to flip your figure upside down. Now align the sole of his foot to the very top of the image border, so it looks like he's walking on the ceiling. This will be your mini's back.
Assuming you are not up to the challenge of creating the back version of the mini yourself, from here it is a matter of finding a method you prefer, to turn this copied upside down figure into a black or dark silhouette, to denote it is the back. Zooming in and outlining the figure within its borders and then painting it all black by hand is a straight-forward but tedious option. There are Photoshop Actions or Scripts or Plug-Ins that will turn images into silhouettes if you have a program that is able to use those. You could even just type "BACK" across it, etc. Regardless of what you decide, you are still not done with this mini's size!
Final Miniature Size
Believe it or not, this mini is going to grow yet again. Now that you have the mini front and back and otherwise ready, you need to add the extra space that is used for the "tabs" or base, for it to actually stand up. This is done by adding yet another 30 mm to the Canvas Size . Image > Canvas Size > type the new size as 30 mm larger than the current (total of 90 mm), and make sure you put the current image in the CENTER of the canvas add this time - you DO want to add white space above the head of the "front" image and above the head of the "back" image, so there is white space at the very top and very bottom of the image. Once this is done, you may wish to either use the Fill or Bucket tool to give this new blank space a visible color, or you could give the now complete image yet another thinner border (or maybe just these new sections), because if you don't differentiate it somehow, when it is printed, you won't be able to see where to cut it.
Assembling the Mini
After cutting out the full 15 x 90 mm mini, you can either use the Inverted-T or A-Frame assembly style:
A-Frame: fold the image in half at the fold-point, so you have a V-shape, with both figures displayed. Now fold the foot sole border of the top and bottom of the image so they disappear around the back of the mini. You may then tape or glue the two blank tabs together, which sit under the slanted A-Frame or upside-down V mini, providing an invisible base.
Inverted-T: fold the image in half at the fold-point, so you have a V-shape, with both figures displayed. Now fold the foot sole border of the top and bottom of the image up against the inked legs of the mini, then pinch the mini together at the foot area, pulling it together into one flat vertical structure, and tape or glue it at the foot area, and also at the base area itself, which should be bent out and providing a flat, extruding stabilizer on each side of the mini.
You may also want to attach your mini to a heavier, solid base, like a washer or coin or even checker or poker chip, using tape or glue.
So now you know - the full length of a printed 25mm mini is actually 90mm, nearly quadruple its original height. I hope this proves useful and helpful to gamers out there. Feel free to comment!