Bathrooms are characterised, in general, as more restricted areas - they are not always the big, airey rooms we may hope for and, often, do not have natural light. As such, lighting becomes more important than usual. Lighting must be more intense than in the rest of our house, as compared with the needs of the room.
You can also choose to have natural bathroom lighting. This kind of lighting option is just perfect for small bathrooms. If you have a small bathroom to the right portion of the house, you can have a row of windows above for letting the natural light outside penetrate the bathroom.
There is no rule such that the bathroom lighting should be provided only in the ceiling or is better if it is provided at the sides or on top of the mirror. One has to fix the bathroom lightings according to one's taste and the mood that he or she wants to bring into the room. Even for a small bathroom, people, these days, go for two or more lighting fixtures. Thus, lighting is the most important factor to be considered in any modern bathrooms.
Also the light can be reflected by using mirrors if they are placed in strategic places and you can get better results when decorating the bathroom. It may also be supplemented by a lamp or lamps perched on the bathroom cabinet if the electrical system allows this. All these will help you to have a stronger light when needed, but also a dimmer light to create a romantic atmosphere.