Dude is making some awesome stuff with World Machine, over at: Environment Work - Work in Progress - Unreal Engine Forums
You gotta do 3d stuff anyway. Why not try Blender (It’s free!) Some tuts: http://www.youtube.com/watch?v=Af6A1uvNhyM
http://www.youtube.com/watch?v=fvGX8ShwzKo
There is so much out there, you’ll find something that fits your needs. Good luck!