This is a simple way to make a temporary tattoo in any design you want. I only used one color per tattoo, but you can totally use more if you want to. All you'll need is an old sheet of stickers (or a piece of paper) and nail polish without bad chemicals. I used Jenna Hipp, but you could also use Piggy Paint. My Jenna Hipp set is a more neutral palette than the one pictured in the link, although I think the bright colors would work better.
Wasn't that cool? Tell me what shape you used!