extend your software so a photo can have popup captions--captions embedded into the photo that appear when a user hovers over or clicks an area.

My idea is to use your software in almost the opposite way you have now. Rather than being able to HIDE a caption, you add the ability to SHOW a caption. Hover over a mountain and up pops "This is Mt. Rainier, which we climbed last week." Hover over a person and up pops "This is Frank, our guide." This could turn into a separate product for you, which would have a wider appeal to the general public.