Military base in the desert - good concept. I like what you have so far. The layout looks like it will make for a fun map to play. Also you've done some really nice terrain work along the sides of the map.
And now for some constructive suggestions... :)
Textures
You probably are already planning this, based on your "somewhat lacking in detail" comment, but it could use a good bit of texture work. Specifically, you might consider changing the texture for the exterior of the base... perhaps one of the more solid looking metal textures. IMHO, the current one is too striped-looking. The same is true for the ceiling texture.
Also, a general rule of thumb I like to use is to try make texture changes correspond to architectural changes. In other words, try to avoid abrubtly changing textures along a flat surface as it makes the textures just seem kind of painted on.
Along the same lines, it's best to choose textures that fit your architecture... or vice versa. One thing that breaks the illusion is when you can tell that a texture has been cut off halfway. It's probably better to just use a smaller texture that will fit the space you have available.
Map Size
I have to agree with Ratboy about ending the map in skybox. To really make it feel like you're out in the middle of the desert it would be best to have the map extend well beyond the fences. Then, to really give the map a sense of scale put some large objects off in the distance using a large gridsize. Ratboy suggested dunes, you might also consider some plateaus. Here are some examples courtesy of the Google image search for creative inspiration:
plateau 1
plateau 2
plateau 3
plateau 4
plateau 5
plateau 6
Fences
I can't quite put my finger on it, but there's something about the fences that doesn't seem quite right. Perhaps it looks too "stacked". I think the part that looks like a gate that opens looks great. I would build on that... maybe if you made the rest of the fence have vertical bars instead of the "X"... and reduced the height by half... it would be a more convincing fence...
Well, there are some ideas for you to play around with. I hope some of my ramblings are helpful and you decide to keep updating the map.