These are great. Very inspiring, thanks for sharing.
Come to think of it, I did something very similar last year on a much smaller scale. I was photographing my great grandfather’s dogtags from the first World War, and wanted a flag in the wind as a backdrop. I had a flag photo kicking around so I displayed it on my iPad, put it in the background, and lit the dogtag with a snooted speedlight camera left. I dialed in the flash exposure on the dogtag, and then by varying the shutter speed I was able to tweak the saturation of the background image. Of course, I had to crop the photo quite a bit so as to not reveal the iPad, but I was actually quite surprised at how well it turned out; what started out as a silly time-killer experiment resulted in a photo that my grandmother now has framed in her living room.