Just based on the pictures, a few things I can see are
-Floor and ceiling textures are too repetitive and don't match. Find different ones. Break the brushes up a bit. Give some variation
-There seem to be no light sources... they're probably just around the corner, but I thought I'd point it out anyway.
-That coathanger/pillar thingy has no shadow.
-I like that fallen file cabinet, but it seems out of scale
-Texturing on the floor isn't so great.
-That light texture looks fugly.
-Looks somewhat washed out. Use spotlights on those lights hanging over the conveyor
-Wall texture is incredibly boring IMO
-That room hanging out is just wierd. Add some borders to that glass and change the ceiling and floor textures
-conveyors add to the lag a lot in HLDM