If your room is a little dull & simple, it's easy to liven up & make schizophrenic & visually overwhelming for around $10.  Just take some random topics you're interested in & get some books on them at the library & look for propaganda pictures (children's books are a good source....) to photocopy out (I suggest keeping any captions) & tape them to the wall & keep layering.  At kinko's you can use different colors of ink to highlight particular items & of course you can adjust the size.  Another trick if you have a particularly worshipable book that you're enamored by, buy two identical copies & tear them apart & paste them up to cover an entire wall & you can refer to the book easily anytime.  Get a book of quotations & copy out the ones you like & paste them over the other stuff.  Depending on how much layering you do, stuff may want to fall down, just hammer in straight pins places where things are especially thick.  You can also shove pins in so you can hang some of those mini-tree ornaments for whatever holiday it is you like or jewelry or Darice Crystal Cuties.  Near the ceiling you can hang up so garland from your favorite holidays or if you're an ultra-punk you can use barbwire instead.  For the ceiling you can use pin technology & colored balloons or trash bags, but be careful by light fixtures cause you can catch things on fire.  If it still doesn't look crazy enough for you spray on some Razzle Dazzle webbing to make it look a little creepier.  if you have a three lightbulb fixture put in three different colored lightbulbs so the shadows are cast funny & hurt a little.  Your room will look like a serial killer's from tv in no time.