yeah - as gecT said, the main problem at the moment is that all of the materials look the same - everything is too shiny. try working on a spec map and concentrating on what objects would be shiny and reflective and which objects are not.

also - your textures just look way too clean and without any sign of wear - especially in a museum where there is likely to be dust and grime.

last - i'd lose the da vinci painting - it's too obvious and too well known - and it would be unlikely that a painting of that size would be hung in such a tight corridor and never with (what looks like) direct sunlight coming from windows on the opposite walls.