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.
Task lighting: Task lighting should allow you to groom yourself efficiently, not create shadows and special effects, although no doubt it's fine if you can easlily incorporate those suitably in your lights arrangements. For task lighting around the mirror, place the light fittings on each side of it. The lighting should illuminate the person before the mirror rather than focus on the mirror. Generally speaking, the lights should illuminate your face fully and minimize shadows under your eyes and chin. It's also possible to wish to install lighting inside the bathroom cabinets so it is easier to consider things placed inside. Also install lighting fixtures over the bath area and toilet.
Ambient bathroom lighting is a very popular choice For providing ambient illumination, the use of chandeliers and pendants are recommended. You need to keep in mind that bathrooms have the presence of a high degree of water vapor; this leads to the cracking of very hot bulbs which are exposed. Chandeliers and pendants have exposed bulbs, so think twice about their placement before having them installed.
The different varieties of lighting fixtures include ceiling fixtures, side wall mounting fixtures, etc can be chosen as per one's taste and requirement for his or her bathroom. Also depending on the size of the bathroom, one can choose from a single light fixture to a couple or more lighting fixtures.