I've heard lighter shades are better for smaller rooms. Also since there are no windows for natural light you may want to avoid a darker shade or too overwhelming/bright of a color. I just saw in a magazine a smaller room being painted all white with the ceiling a bright green shade that matched a curtain in the room. It looked really neat. I'm not sure if you would want to paint a ceiling though, but it was sharp. Not sure how that translates to a little bathroom either.