Well first, it looks like you just made a large room and threw some prefabs into it. I know that those white/grey cage style boxes where made by VNVNation.
You need to credit those people. Also try to make some of your own stuff to add to the map.
It doesn't make it an better that there is no lighting and all the textures are about the same color. It's too hard on the eyes.
The layout is pretty boring too, just a bunch of boxes in a long hallow room. Very few fun gameplay elements in this map.
You could've used some more textures, added a skybox with a light_environment to make things a little better.