First check out this image:
Material Editor Settings
Under Blinn Basic Parameters you can enter a number from 0-100 in the Self Illumination box. You should see the texture get brighter in the scene and the material editor.
I've always used a value of either 0 (default) or 100. I don't see any reason why a value in between would not work. I've always used this setting for lights that I wish to have a brighter than normal intensity and it does make a difference in game.
Here is how it looks upon initial export in the lighting tool:
Lighting Tool
Just place a point light nearby so it hits all the vertices of the light polygon and you're good to go.
Finish up, export and launch the map in game:
In Game
It is pretty obvious that it has an effect.













