So far, it needs alot more detail. For a detailed house, it needs that material based feel to give off realisim. The colour I would change however that is just my personal prefence. If you looking for examples of past work of barracks here is one - Rate my build x/10
To further my point, as this looks more like a starting building and not a finished desgin at all. Is to sorten the windows, and not have too many at least within the mid structure. Apart from that its a good start.
For the exterior, you should add more detail, like adding pillars. You should also make a bigger doorway to enter the building. Overall, this has alot of potential!
I personally don’t like a bigger doorway. It can already fit R6 rigs quite comfortably. Pillars don’t really work however I would add an interior to enlighten it.
I don’t necessarily know the origin of his group. But from the standpoint of a modern, realistic military, I wouldn’t do this. Banners are kind of tacky, and they may remind some folks of some particularly angry Germans ‘round the mid-40’s.
Then again it depends entirely on the genre of military. If you have more of a sci-fi or overbearing government type situation, banners would work (although I’d recommend making the logo out of parts or a mesh, and not use decals).