The moon is nice. i dont know if it fits into the "everything should look real" layout, but i also dont know if there will be more stuff like that and the whole design will be founded on style rather then reality.

the levels look quite dull so far. without you telling us its a swamp level i would never knew it. the inside rooms aint that interesting either.
I assume there will be some lightmapping later on or at least some shadows. this might add quite a bit to the atmosphere of the whole project. so far it looks more like an A5 game.

I like the zombies and the weapons so far as well as the moon.
hope there will be some unique gameplay features so you can compete with left for dead and all the other zombie shooters coming up.

good luck and have fun
cheers