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.
Bath lighting must meet three conditions: to be functional, aesthetic and to have a special ambiance. For the daily tasks (shaving, make up, etc.) you needed a strong light and for moments of relaxation, such as a bath in the tub, you need a discreet light. Also the bulbs that you use must provide the amount of light needed to properly light this room.
The mirrors in the bathroom should reflect as much natural light as possible, also, artificial ones, if placed in front of windows, will reflect the light giving the impression of a wider space. The bathroom light must be clear, with controlled intensity and not bright. What ever lighting you choose, it must work with the furnishings, mirror and other decorative pieces placed in the bathroom. A classic style bathroom must have mirrors with elegant frames and shaded lighting bodies . For modern design choose mirrors without frames, spots placed strategically so that the light is not too bright.
By using light fixtures with dimmer control, you will alter the intensity of the light to get exactly the required relaxing feel. Dimmers are also energy-savers and your lights will last longer. Just keep in mind that you would need incandescent dimmers for incandescent and halogen lights and agreeable dimmers for any other kinds of lights.