You mean like, have one texture here, another there?
All you need to do is edit the terrain mask with another color where you want the different texture to be.
For example: Say I'm making a map. I go to a new, non grayscale image of my height map, make a new layer below the terrain, color it green, decrease the opacity on the terrain so I can see the green but also the terrain still, then I just color in using pure red or pure blue (Or both) where I want the different textures to be.
Hope I helped you, floof!
