Welcome to Polycount! For the column normal map, try flipping the green channel. For the building UVs, take a look at modular techniques. http://wiki.polycount.net/CategoryEnvironmentModularity
Can you show us the degree to which you broke down the assets to acommodate modularity. Loving the touch with the glowing eyes at the end of the tunnel.
Not sure if this was posted, but this is AWESOME reference for modular environments. There's a LOT of images and instructions deep in here, be sure to look around (projects page) http://www.hirstarts.com/
nice! keep at it. Your cobbles seem a bit melty/smooth, maybe the specularity map needs adjustment, I'm not sure. IMO rocks are really much more difficult to make than they seem; eons of geological history is required to make each rock. If you search for cobble there's a few good examples you can look at…
Check out Kevin's post about GOW2 bricks. Gears of War 2 modular modeling More here. http://wiki.polycount.com/CategoryEnvironmentDesign#Modular_Design_and_Workflow