I don't see why someone would have a problem with someone else storing an image on their computer just to view. If your photo source wants to be protected against someone using their image for profit, use an editing tool to include a copyright written onto the image. That's the only way I know of to protect an image file. While it does make the image different, it identifies the source, giving the person who originally made it some protection against the image being used against their will or without compensation.

Bob