Another option is to try theme decorating. Make your own Cajun bungalow with Spanish moss, taxidermied gators and fishing tackle. Hedonists may opt for some nice fur-lined walls, or perhaps velvet, accented with various leather implements. Once your walls and floors are jazzed up, you'll need to move on to the little things. Try some throw pillows in different colors and textures.
Plants are always good.
Be sure to check the tag for a plant that likes low light and doesn't need to be watered often. Or just ask the sales person for a cheap plant that is impossible to kill. You can't beat homemade decorations. Get your roommate, or even the whole floor, involved in a project. Save up all the caps to your beer bottles and make a collage.