Looks nice! I know what map this is based on
Probably should add some sandbags/cover for the gatehouse.
If you are up for redoing it to reincorporate scale, and streamline the recreation of this map you could screenshot a vertical viewpoint of the map, and then convert it to dimensions of powers of 2, and then import it as a .png. of course you'll need to figure out a scale from the texture that fits the actual size. (50x actual dimension size).
A few suggestions.
Nice utilization of BSP, however, BSP usually isn't designed for art assets, unless you need fill in a gap, or say the walls of a building. It looks bad if it's trying to represent complex geometry (even fences) and it is also less efficient than using a mesh in most cases.
So I'd probably remove the concrete fence on the second photo, and replace it with something else.
It'd probably be better to utilize meshes for those cliffs too!
Increase the tesselation of the terrain. At the moment, it doesn't look too natural, ie the pointed vertices.
Aesthetic suggestion, find a different, dark less "vibrant" grass.
(Maybe some bushes too?)
You can find more materials for terrain here:
C:\Program Files (x86)\Steam\SteamApps\common\Red Orchestra 2\ROGame\BrewedPC\Packages\EnvironmentalMaterials
and here:
C:\Program Files (x86)\Steam\SteamApps\common\Red Orchestra 2\ROGame\BrewedPC\Packages\Props_Static
and also here:
C:\Program Files (x86)\Steam\SteamApps\common\Red Orchestra 2\ROGame\BrewedPC\RSGame\Packages\EnvironmentalMaterials