Some ideas..
1. Forest map but on a scale that shows it could only be on an alien planet. Trees would be like huge buildings that dwarfed the mechs. A lot of the foliage would be high above you with the forest for being less complex to make the engine handle it better. The tree trunks would be huge and the canapy above would let in bright sun in some places and creat shadows in other places. The forest floor could also have ancient ruins like angkor wat with its giant faces and tree roots growing over and around buildings.
![Posted Image](http://scilib.narod.ru/Other/Cinefex/images/102.jpg)
![Posted Image](http://i.ytimg.com/vi/BeOxf3nIVsg/0.jpg)
2. Huge scale alien city. By this a mean a city where the building giant and you are moving and fighting in the confines below them. In this area at the bottom you can do a lot with levels. Train tracks that go through and between buildings. Road ways that go under around and through buildings. This would also be a good map for lots of interesting neo lighting and signs etc.
![Posted Image](http://www.ukipdaily.com/wp-content/uploads/2014/02/blade-runner.jpg)
3. Truelly strange alien landscape. This would be designed to make it very clear you are on a strange alien planet unlike anything you had seen before.
![Posted Image](http://31.media.tumblr.com/125c48ab456963d4161ad27543ce79d9/tumblr_n1tdn1ePKF1qcsz65o1_1280.jpg)
3. A giant space ring style space station.
![Posted Image](http://thefocusedfilmographer.files.wordpress.com/2013/08/elysi.jpg)
4. In and around a massive crashed ship.
![Posted Image](http://www.imaginefx.com/02287754333273104115/main.png?a=0&maxh=400)
More to come and please share yours.