Models from Sketchfab,

Skeleton Rig: 

https://sketchfab.com/3d-models/skeleton-character-psx-ece576bbed4b4364911c7596d828a558

Buildings: 

https://sketchfab.com/3d-models/building-city-apartment-building-75cec2fa0cb0470d9d1972982ef2191b

https://sketchfab.com/3d-models/city-apartment-building-536b0f079fd6420f964f93f6fda54f08

Fenced Platform:

https://sketchfab.com/3d-models/building-metallic-protective-fence-low-poly-3ff781b593a94b4caf993546804449be

https://sketchfab.com/3d-models/garden-cement-fence-wall-building-19d283b94d664ef4ae3eab99d17cc00a

Warehouses:

https://sketchfab.com/3d-models/small-warehouse-2-1420588322d34ec3b25423bf055398da

https://sketchfab.com/3d-models/long-warehouse-73da0b497eb44e4e972d297db8f88bb3

Trees:

https://sketchfab.com/3d-models/oak-tree-3dc59560f2d24345bdbe65c44636453b