I'm not a pro mapper but you asked for some feedback, so here it is.
What is good in this map?
-the general lightning is good
-the screenshots gives enough information about this map.
What I don't like.
-don't like the skybox
-don't like the grass
-don't like the flying building
-well, I don't like the map
To make this map better:
-change the skybox (like militia_hdr)
-paint the grass and don't make it flat
-put some props in it (like a bush)
-the map isn't detailed (maybe a little bit water in the middle or a pool with some propsaround it)
-play with light's, so you get nice effects.
-don't forget the env_sun.
I hope you can do something with this, and happy mapping!