Essentially, all you need to do is pick up some decorative paper (the awesome quirky dog paper in the photos is wrapping paper from Paper Source). Line it up carefully, and attach it to the walls with small thumbtacks annnnnd... you're done!
Seriously. That easy.
And look how cute and unique those dogs make the whole hallway look! Larger photos at Apartment Therapy.
Oh, and if you have extra paper left over? Why not try updating some of your old dorm furniture with it, like so?
Is that beautiful, or is that beautiful? You could do this with contrasting, matching, or complementary papers for a whole host of different looks. (Instructions here).