Hi OP, the stuff you've made looks already quite professional, so I guess most of my suggestions would be obvious to you, but I thought I point them out anyway, just in case you missed any
In general, I think that the buildings lack colour depth. Shadows and shading is done with grey, which kinda kills it a bit, and make things look boring and artificial, but I think that would be fixed to some extent when you will adjust the real time lighting in the game with some coloured sunlight and ambient light.
Nevertheless, Making sure that there is some subtle colour variation will really help making things more dynamic.
Regarding the vehicles (didn't feel like doing a paintover for those):
- Since they're huge tanks, the worn edges are a tad too big by comparison. It makes them look small.
- The tanks are pretty much dark grey spotty blobs with some colour spots on them. It would be good to unify the look, reduce contrast and have detail in some key areas, while reducing it in others.
About the building, I added text in the image.
Good luck with the game. Hope it will work out with the textures!