Going from what you guys have said, I've added lights to the top of the walls to make their shading more relevant. When I originally did the walls I did it as if the light source was at the top of the wall/ in the roof and didn;t think to actually show the light. I also changed the floor to be plain cement but I've noticed in stores etc that cheap floors tend to have a lot of speckles in them so I've done that to add a little detail. I also put the yellow lines in.
On Argyle's reversion the lines are where the crates would be placed, in the warehouse of the store I used to work in, we had yellow lines which meant "leave this clear so we still have a walkway" if that makes sense.
This is how it currently looks.
I love the amount of constructive critiscm you guys give, I've never known a forum where everyone is as in-depth and helpful as this. On other art forums (where I post my drawings, concept art etc) people just say "It's good." or "Fix this." without really offering anything to the mix.