Bridge Over Troubled Water

I'm making some tests for the new graphics. I'm not satisfied with the raw conversion from a bmp to vertex colours, so now I'm experimenting with a raster to vector software: I take a bmp of a piece of terrain, I vectorize it, then I rasterize the vector, then I apply this "vec-ras" image to the vertex colours. The result I'm seeking is something like a cartoon-style map.