Cold Hall image - JustDaveIsFine

Details!

Perhaps sneak some pipes in there, and small support beams of a sort. Small debree on the ground, like a small can or cardboard box or two.
It also looks a tad repetitious, try putting a door, or odd architectural features in there to break it up? (Odd architectural features like a raised roof in some areas, or some walling from another room jutting into the hall.)

But, if you're trying to keep it simplistic, perhaps stick in a secondary light source, like an odd blue light down the hall, or maybe one coming in diagonally through the roof from a shaft that leads outside.

It's really looking great so far though.