And... please correct me on this if needed... the image would only be used on the same device the image came from, or an exact duplicate device: correct?
Mostly, yes. Some applications like TrueImage promise that you can install TI on a totally different machine, and then install an image on that machine from something totally dissimilar. I don't know that I would particularly like that, because then you need TI to be the in-between layer between the image and the hardware, for driver purposes etc.
But mostly I would say an image is intended for use on the same (or identical) machine on which it was made.