Welcome to the forum, Bryan. That's a nice looking object, and I would very much like to see it in a Terragen environment. But what do you mean by height maps? In TG you can import displacement, or rather bumpmaps, as with RayTraced objects on real displacement does not alter the mesh. I don't think you would need real displacement though, bump would be enough. In the default shader you can import color, displacement and opacity maps, and vary those by adding a power fractal led through a transform shader (set to world position). I think normal maps are also used to get the bump working, but it's best to just try it out.
Bump maps can be 8-bit greyscale maps, btw.
And if you really need real displacement, you can turn on forced displacement in the object tab, but for proper functioning, the object would need enough vertices.