Black is very bold color to use in bathroom. If you will make bathroom walls completely black you can get a quite moody place which looks modern but isn’t practical at all. Combination of black and white in bathroom design is much better because it also make the room stylish but in the same time more cozy.
Here is another idea of how to design your bathroom with black and dark gray tiles without making it dark and creepy. This bathroom is 8.3 m² and have an access to a small terrace that lets natural light in. It also visually expands the room. In case you like dark ceramic tiles this idea might be really useful to you.