It is important to have a source of light in your bathroom, to make it more convenient for use for the day and during the night. A bathroom with a large window pane is very useful to have in such a facility, because you can rely on the natural light and minimize the cost of using electricity. On the other hand this solution is for the day and for the night; you can consider to have multiple chandeliers for your bathroom to create enough light. It also depends on where you want them to be placed, either on the ceiling or near the mirrors to create more reflection for the room. That means you can use bright colors to paint your bathroom or used dark colors and add more source of light.