I've noticed that when using surfacelight and lightimage in textures, it creates a weird inconsistent effect. Round lights are showing up on the surface that emits light. Makes it hard to find the right mood!
Here are two screenshots with an exaggerated surfacelight value, to show it.
Shader (non-exaggerated version):
Non-exaggerated screenshot: https://dl.dropboxusercontent.com/u/...facelight3.jpg
I'm aware that it uses itself as a lightimage. This is so that the texture that is emitting will be affected by the light in the same degree as its surroundings (ideally..!)