What resolution did you download your base concrete texture at? I don't have a payed account on CG Textures and I find there maximum size is usually enough. You could probably improve your existing textures a lot by removing the dark seams in the concrete texture, it makes the tileing more obvious.
I would suggest using the entire 0-1 UV space for the repeating concrete wall section and moving the other textures to a different texture atlas. Repeating the texture in the material will give the same effect and eliminate the need to waste texture space on a repeat of the same texture in multiple places.
Its hard to accurately evaluate your textures with such flat lighting. Do your textures have normal and specular maps? If so then its best to import your scene into a game engine like UDK so that we can see how it looks in-game. The only crits I can give you now is that your concrete base texture is a bit too tiled. A…