[McBeige]

If the FoV is less than 180deg then any image would be a realistic solution as long as it doesn't depict anything from the original.

[egypturnash]

My intent here is "same subject, but now you're standing on the other side of it", not "same viewer location but turned 180º".

For instance, if you started with an image of the Washington Monument with the Lincoln Memorial in the background, the "reverse" would be an image of the Washington Monument with assorted Smithsonian museum buildings behind it. Or whatever you theorize would be on the east of the Washington Monument if no reference is available.