Good news: Have an algorithm that generates a texture based on position info. Once I create a nice function to procedurally generate height, also based on position info, I can use the same function to generate the texture that will be seen from high up and seemlessly blend into the tiled terrain. Atleast that's the plan.

Bad news: That damn seam. Not sure why but for some reason the edges seem to be wrapping by one pixel. I've outputed the generated textures to file and they are fine so the problem isn't there. I'm too tired to figure it out now.