I think the alien trees by that crater would be a great idea :)
Maybe use the "floor" alien stuff that also came with them. I forget what it's called. You could either make the crater itself that color or put patches of it around the trees.
I really like those alien trees but not many people use them...unless you put the trees on/around the science facility?
Also, have you used the simhenge, rock with the alien cave paintings, the rocket ship, bridges/archways from WA etc? I don't remember but I know that some other people have included them in their worlds.
