I worked on a set of 3d models. I hope it will be useful for your game in creating environment.
Some of my 3d models were used by my friends in their games too. If you people like my 3d models feel free to comment. also you can find my other models in unity3d assetstore - https://www.assetstore.unity3d.com/en/#!/search/page=1/sortby=popularity/query=publisher:431
Here are my free 3d models that I uploaded in sketchfab: