The RC LIVE Environment node.
For a comprehensive technical description of the scene background in Arion, please refer to this page.
The same RandomControl LIVE Environment node described here is used to configure the background (wallpaper) of the scene.
Render which makes use environment lighting and a screen-mapped backplate.
It is common to use background mapping and environment lighting together, usually in combination with Arion's Matte Floor (or a shadows AOV). For example, the car image above was created with a mid-resolution HDR environment map and a high-quality backplate photograph carefully taken at the same location so both are coherent in terms of lighting and reflections. The Matte Floor feature was used to integrate the car model in the scene seamlessly, so it casts proper diffuse shadows on the floor of the backplate.
For more information on how to configure the environment lighting of the scene from the RandomControl LIVE Environment node, please refer to this other page.