well... it looks a little bit bland, and uniform in texture. mix up some wall filler into a wash and paint it over everything and paint some grimy discolouration and rust around welds, joints, rivets, etc. Finally some brightly coloured markings, text and insignia are good, even the old yellow warning stripes! The other thing is unless this project is for a specific scenario, it's a little large and inflexible, I would make smaller pieces with more varied uses. maybe make the courtyard, blockhouse and towers seperately, so you can MAKE this set-up without being stuck with it.