How can I make my bedroom cool and unique when I live in an apartment?

I live in an apartment (duh) and I want an awesome bedroom, but we can't paint the walls. Does any body have any ideas what I can do to make it more cool and awesome? I'm not sure if we can buy anything, but if we have to buy something to make my room better, than it has to be under at least 75 dollars or so.|||Depends what you are into. If you're into music put CDs on the wall. You can get them cheap like the CD-RW ones and just stick them on you wall in patterns.