Usually we see a bathroom like a very light space, yet sometimes it could be better to use some darker colours, for instance, to use dark tile in the small bathroom.
Let’s say, you don’t have to make all the bathroom space with dark tiles although it is also possible. But it is much better to add some dark tiles into the generally light picture, or maybe you can combine darker and lighter tones of one colour to play with such difference. The ideas of using dark tile in the bathroom maybe helpful in the making the space visually bigger playing with contrast of dark and light: you may highlight the space by making shower booth dark while all other bathroom walls are light.
It is not necessary to create your own ideas about bathroom design, because nowadays there are now so many various magazines with great and professionally done pictures of bathroom design.