I picked a random record out of a huge stack of old records we had sitting around, and started drawing on it with a gel pen. It turned out pretty cool! It looks better in person, the ink has a depth to it that you can't see in the picture. I used one color, it used up most of the pen :) You could try using multiple colors for a cool effect. It took a long time, it's easy but kind of tedious, and your fingers start to hurt pretty soon. You have to really work with the ink on the smooth part of the record to get it to show up right.
I might make it into a clock, I can't think of what else to do with it besides just hanging it up!