I've just started reading about this UGP stuff and its really mindblowing! Man, this would be cool!
Anyways, I had an idea I thought I'd share. What about a planet/land that has a dark side and a land that has a light side. Of course, the terrain would reflect whatever side its on (dark side with spooky forest, dark ocean, etc).
To seperate them, there is a great wall, just like china's great wall, and carved into this wall throughout the entire spanse of it is a relief representing light vs. darkness, similar to the one in palpatine's office in E3. (This could be done by someone who is good at sculpting, or could even be done by casting lots of figures into one giant plaster cast.) At points, there are towers on the wall with guards and a giant iron gate nicked, charred, and dented with battle damage.
anywho, just a thought I'd run by ya'll. Let me know if I could help in any way.