Good to see some progress on this map.
You should add displacement snow to other areas like the helipad too, otherwise it'll look to flat.
I still don't like the wall textures, it needs more variation for sure and also should be darker.
I'm thinking of old natural stone.
Maybe you can find some good ones here:
http://www.cgtextures.com/textures.php?t=browse&q=2 Also the outer wall and the base of the walls should have much bigger stones then the rest.
The higher you get with the walls, the smaller the stone size can be.
