Thanks to Sketchfab to exist.
I used this model to create a matte painting and a camera mapping (you can see the final rendering here: yondasable.deviantart.com/art/…
Models have been downloaded on blendswap.com
Low poly tiny planet CC-BY kavabanga blendswap.com/blends/view/73246
knetmonster CC-Zero Zuendholz blendswap.com/blends/view/58531
I work with Maya but the models are blender files. So I export it in .fbx for rigged characters or .obj for props.
Ill soon write a tutorial to explain my own workflow matte painting / camera mapping.