You can break a small room, but first you must know rules before gaining wisdom for breaking them. You should first study design of a small space and then only seek for incorporating rules into it.
Like in this bathroom, it sticks to neutral color white, which is great for rooms having small spaces. A compact bathroom design must be smart design because possibly there is not a single room, which requires functioning like a bathroom does. After all, you are not required to entertain or cook but you certainly need a bath.
There are definite rules of decorating one small bathroom, but in right space, one can break these rules. It can be an advantage to you if you hire one designer, who knows exactly how much space do you need for door swing, legroom, etc, and is able to coordinate one fully functional bath, which can fit in space available to you.