Yes, I agree that the skybox should be changed... As much as I like the texture you used for it, I think it's way too bright for the darkness of your level. If you could maybe darken the sky a little bit to fit in with the ambience going on, that'd work out nicely.
I was a little "blinded" (if I can even USE that term for looking at a screen, lol) by the skybox and couldn't tell much else about the level, but from the silhouettes I can see, it's looking very interesting, lol.
Good luck out there!
The one and only,
~PlystirE~
Dammit, Jim! I'm a programmer not a graphic designer!!!