CocaCola,
I haven't used any actual shaders for the level yet. At the moment, I've kept things simple. The walls, ceilings, floors and models all use a basic material effect.

Code:
MATERIAL* mtl_walls =
{  
	ambient_blue = 40;  
	ambient_green = 40;  
	ambient_red = 40;  
	diffuse_blue = 80;  
	diffuse_green = 80;  
	diffuse_red = 80;  
	specular_blue = 0;  
	specular_green = 0;  
	specular_red = 0;  
	power = 0;
}


Aside from that, the player has a dynamic light used as a lantern and the level fog sets the view distance.