Trying my hand at Arch.Viz. Model-AutoCad 2009, Render- Keyshot 2
Good start. I'd add some rough texture on the materials for the brown walls, white corner stones, and white foundation. Try the cast iron texture as a bump map - with the right settings it should give a stucco effect.
Also try changing everything that is pure white to off-white.
You'll see a big difference.
Ed
what lighting environment is that? the conference room?