While i was looking at OpenGl books and stuff (that can be found around the net) i found, that what i was looking for can be done in GLSL without the need to touch the engine c++ code, but of course Gl_Decal could be added and multiple to the blending and stuff with just a simple line of code, but anyway. So yeah, a tut about how to use the glsl with NeoEditor would be nice to have for in the future!
How about: Deferred shading
Deferred shading wiki
That would make the engine have a next-gen lightening.