Ok, so this is sort of a Harry Potter Question?

Ok, for the premiere of the seventh Harry Potter movie, me and three of my closest friends are going to throw a premiere party. After wards, we are going to the midnight premiere. We were originally going to dress up, but we can't anymore, so I decided to hand-make four t-shirts using t-shirt paint. Anyways, I would like some ideas of what to put on the shirts. I want to fill them up as much as possible, and I need some really cool and awesome ideas of things that would make the shirts, well, awesome! Any ideas are accepted!