When I get stuck, I usually play other games and get inspiration from that. I'm working on a place now based on a region of World of Warcraft (After I started the map groundwork, the idea and layout started to change from the original concept of course)
Here's a hint I've worked by, but I dont know if it works for everybody:
A map (like any other creative work be it a book, movie, or video game) has a life force and grows on it's own, if you let it. Most people try to speed up the development or alter it in a way that they personally like. This isn't a good thing to do. You have to flow with a map for it to turn out it's best. Just let your heart tell you how it should be done. The trick to creativity, you (at least some deep, distant part of you) already has finished the idea, your just reading it for the first time. (Another way to think about it is that somebody else made it and your just trying to bring it into this world for them)
I dunno, this method works for me. True, most of my maps get strange towards the end, I can't predict how they develope. I may have a good idea, but for the most part I'm in the dark.
In your case, I'd look to other good games for inspiration. (Halo 2 is a good one lol)
some one help me 
