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.
The bathroom lighting contemporary task light, serve to provide light for the various grooming functions that are carried out in the bathroom. As a result this category of light focuses on the vanity area, shower stalls, or over bathtubs and toilets. Sconces or vertical fixtures on both sides of the vanity, or that center mirror that you use to shave, brush your teeth or put on makeup are excellent task lights.
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.
Remember that different kinds of bathroom designs require different kinds of lighting. The lighting you choose for your bathroom will be largely dependent on the room design, personal choice, as well as the bathroom setup. Make sure that the lighting in the bathroom is just right, not very bright and neither too him.