I have developed a very simple anime light set for Poser to achieve desirable effects when cel shading anime. Typically, anime cel shading puts the same tone across all of the skin, except for a darker toned edge, close to the outline. This edge is usually very thin and all the way around the character, although that is certainly variation. When cel-shading, this effect can be achieved with two light sources. First you need to add a single distant light source shining directly from the viewer’s perspective toward the character. With a photorealistic render, you want to simulate ambient light with light shining from all angles or by using Image Based Lighting (IBL). Its not the same with cel shading. If you did this, there would be no darker edge. The shading would be all one solid, flat color. With cel shading you only want light shining where you want to see the lighter of the two tones, and with anime that is usually head-on. Basically, this single light is all of the ambient light you need.
If the character is outside, or in a room where the light source is overhead, then you also need to add a light coming from directly above the character. This is because you don’t want any dark toned edges on top-facing edges of your character. If you did, it would not look like the light was coming from above.