Love, love, love this. The building etc are sublime, the others have said enough about lighting, so I won't bother. my one gripe is that sand, it does seem a tad too orange at present, especially with HDR. Maybe consider toning down teh saturation a teeny bit, darkening and putting some more yellow in? Also think you could definetly get more barrels, carts and stuff in there without it getting implausible.
I dare say that a full on muddy, rainy, Deadwood look might work as well, but that would probably require a great deal of re-working.