No there isn't. The "background" is "written" onto your image as a separate step, before rendering. Then the render is layered on top, as a 2D image manipulation, much like layers in Photoshop. The background is not part of the 3D scene and is in no way visible to the lens.

However, that doesn't mean you can't have an image or movie in your scene, behind your subject. Place a one-sided square, suitably positioned and scaled behind your subject(s). Then place whatever imagery you want on that object in the material room. For self-lit backgrounds, connect the image or movie to Alternate_Diffuse or to Ambient. If using Ambient, set Ambient_Value = 1. In either case set Diffuse_Value = 0 and Specular_Value = 0, so that no part of its appearance is influenced by lighting.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)