I used contact paper in my dorm room, and it came off totally fine. But I only put it up on my closet and doors which were all made out of that fake wood stuff, and I had a bunch of small-ish cut outs rather than wallpapering the whole thing, so I can't vouch for large areas. I definitely would not have used it on painted surfaces, though.
Another thing that worked out really well for me was putting up big pieces of fabric. I found 2 yards of this awesome sunset-colored gradient gauzy stuff, and put that up along with a big palm tree that I painted on a piece of posterboard. It turned out great, and was an easy way to cover up the oppressively bland wall colors.