It looks like you really have some cool details and stuff going on in there, but it's so dark I can't see it.
You may want to consider upping the brightness of your lights some. You can still have a scene with lots of dark areas shrouded in shadow, but the lights should be really bright to illuminate the areas around them.
I've been doing a lot of work on this with my current map to get the right look. A good way to see if it works is to jack up your mid-range colors to 1.5 under the view->world options -> post-processing. If your bright areas still look bright, then you have the right balance of bright lights and dark shadows. If the lights aren't bright enough, the lit up areas won't stand out as much from the shadowy areas.
Edit: Also, the outdoor areas appear to have orange light cast on everything, but the skybox looks grey? What is casting the orange light?