Is there a possibility to add a shadowmap from an additional texture that will not be tiled like the other textures do?

The template terrain shader from Gamestudio does this with the blue channel.

This is a nice addition to paint or bake static shadows at your terrain.

I'm currently working on a terrain shader, that will combine some of the terrain shaders out here. It will also contain shadowmapping, but I need a few days to finish it, so if you can wait...
If not you can simply use the alpha channel of the blendmap in this shader, for the shadowmapsupport.

and how many colors texture you want support? That would be great if someone can make one with support 5-6 or so ^^, but i dont now what FPS and graficcard say to that^^

I'm planning a maximum of 8 textures, this is possible, but of course needs more performance.