Wilbur is a terrain painting program that creates nice looking terrains by user specifications. It is really easy to draw/paint a terrain landscape with heightmap which then can be imported into WrpTool.

Only issues I got with it is that the 4096×4096 sized terrain drawing is extremely slow in my computer and that the saved .ter files arent working really. Hopefully these are fixed in v1.62 or will be fixed :)

Download here.