I did this once when I was a kid at some afterschool art classes I used to go to. This thread totally inspired me to try it out again. I made these for my sister's twenty first birthday - her favorite drink is a cosmopolitan. I kind of had to skew the original shoe image I had to make it look right on the martini glasses - but it was fun figuring out how to make it look right on the funny shape.
Oh, and to answer the question on the last post - the little bottle I got which is not quite half gone after doing these was $10 at A.C.Moore (which is kinda like Micheals, but better IMHO).