Yea, you need to update your ambience. Also your sky cards don't match the lightness, hue or saturation of your skybox. You should probably use cliffs and hoodoo's to obscure the low horizon, but with the new skybox you could probably just get away with a desert, if you're careful in its execution.
The middle building needs more detail, and where you have those conveyer belts enter the building with the doors onto the bridge, you could bring that building out by 256 units. It seems fairly flat as is.
You've probably had enough people tell you this but in an effort to motivate you to change it so it's more unique, right now it looks like Fastlane crossed with Mainline.
You've also fallen into the same trap as with Mainline/Reelfoot in that your placement of the dirt tracks is illogical. Your dirt tracks overlap the corners of buildings, and stop at arbitrary buildings/walls.