From briefly looking at the single picture you posted the map feels flat with sniper sightlines. It also seems you arent mapping on grid from the few sloppy brushes I can see in the picture. Something I suggest it look at how to do terrain height variation aw well as building variation. It's a good start and you definitely have something to work with here. DO make sure you are mapping on grid and slap a few heavy props in there to help with scaling while mapping in hammer.