Things to hang on the wall -- I want your ideas

A little background for you... I'm a freshman at the University of Kansas this year. I moved into the dorms mid August. Since then I've hung a few things on my wall, (pink floyd poster, swimsuit calender, and periodic table of elements (I'm studying chemistry)).

My question for you is, what else should I hang on my wall?

Getting some car related items up would be awesome. The only stipulation is that I want to spend no money if possible (college kid, remember? ;) I've got no money!)

Thanks for your input,
Sinister.