So, I'm walking through the Walmart the other day, and I notice the machines for digital photo prints have lowered their rates. You can now get a 4x6 printed immediately for 28 cents, and sent for bulk printing (a couple day turn-around) for 15 cents each. Other local stores may offer a little better rates, so shop around. Curiously, prices go up exponentially with each standard size increase.
I checked on-line and found outfits like Snapfish which may be a couple cents less per print, but require uploading your pictures (which can be huge) and often require pre-payment. Also, by the time you add shipping, the savings are minimal.
I began thinking that 2x3 is only a little smaller than a standard game card. I measured cards from Uno, Buzztime Trivia, and a standard playing card, and they were all around 2.25 x 3.5.
So, since a digital photo is just a jpeg on a memory card, one could create a card in Photoshop, Gimp, etc, upload it to a memory card, and print it on one of these machines. You would just need to duplicate the dimensions a picture (my 3.1 megapixel camera creates images of 2048x1536, giving a better than 300dpi (photo quality) print at 6"x4"). Then put a line down middle, and place two images side by side. For single-sided cards, this would be two fronts, and for double-sided cards, this would be a front and a back. Load the file up on a memory card and head off to the print machine.
I'd suggest making a couple prints at the "print it immediately" machine, to check out your designs before shipping a whole batch out for remote printing. While you're at the store, hit the craft area and look for a corner rounding punch (around $5-$10) to finish your corners. If you're making double-sided cards, pick up a scrapbooking adhesive dispenser (around $10).
When you get the pictures back, cut them in half on the line and punch the corners. If you're making double-sided cards, apply a strip of adhesive along the two long edges on the back of the front card and a single strip down the middle on the back of the back card. Then, line the two cards up and stick them together back-to-back. I tried folding the 4x6 in half, back on the line and sicking the halves together, but the halves would keep trying to pull themselves apart near the fold.
I found that the single-sided cards feel close to standard cards, and slide off each-other pretty well, but they are not as stiff and don't have the 'snap' of standard cards. Depending on your personal preferences, these might be best used for things like trivia cards, Monopoly property cards, etc. These cards would work well for play testing.
The double-sided cards shuffle a little better, and have the stiffness and snap of playing cards, but may feel a little too thick. Since they will cost twice as much per card, you may wish to save these cards for demos and samples when submitting your idea to publishers.
