I have found an easy way to fake back lighting in the blender game engine. I have only tried it using GLSL but it could be possible in multitexture mode some how.
This is the resulting effect: (exaggerated for effect, It can easily be more subtle)
To add a rim shader effect to a material is actually really simple. First create an image like this. The softness of the circle is what determines the softness of the lighting. You want the circle exactly in the center as this gives the most even final result. Mine is a rough example for testing. You would want a better one.
-Now create a texture with this image in the material you want to be rim shaded.
-Next select “Nor” for normal in the “Map Input” tab
-Use Size X and Size Y to adjust the size of the rim. In the above image I used .75 for both with the example texture
-Now go into the “Map To” tab and de-select “Col” (colour) and select “Emit”
The result is that the object emits light around the edge as well as reacting to lighting in the scene creating an impression of back lighting