If you ask me, the simple textures compliment the extravagant architecture. The two go well together to cement the behemoth palatial chateau mansion theme of the map, and make it clear that the game is taking place in the time period, and not years after. With less contrast in the texture on the wall, the actual shape of the geometry becomes the focus. When so much attention is paid to the geometry, which is not boxy or reminiscent of FPSC in the least, its not a wonder that this game looks so nice. if you must add more crust and grime to the textures (something I notice is more of a mandatory addition than a style choice, especially in non sci-fi games around here) then you should add it tastefully in the corners where the floors meet the walls and maybe something where the walls meet the roof/ceiling. I would suggest not doing this at all, though, as the game looks fantastic as it is.
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