Hmm. I think I would put the first render on a simple plane, image map connected to ambient, and put the plane where the render should be. A cove would work as well, but may distort the render. But putting something with the first render within the picture should work IMHO.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

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