This is the Unity version of the modular tech environment I built earlier. 500 something pieces makes for a fun level building time with this set. Works well for top-down or first/third person type games too.
You can find it on the Unity store here: https://www.assetstore.unity3d.com/en/#!/content/107052
The pieces are built to accept just about any type of material and tiling textures, so its easy to adjust the whole set to whatever look you want. Works well with PBR or simple materials.
You can find the Unreal version here: https://www.unrealengine.com/marketplace/modular-tech-environment