I just read the remarkable piece of journalism about the woman who was the subject of this famous photograph:in the Washington Post (h/t LGM), but if that link hits a paywall for you, you can also find it in the Anchorage Daily News.
But it occurred to me that it is, in fact, an example of a small little niche genre: stories about the lives of not-particularly famous people who appeared in famous photographs. A few more examples occur to me.
First, there are stories about this other famous photograph from the Vietnam War, in which American napalm, dropped on children, has burned off the clothes of a little girl:before) of the girl—how the photographer rushed her to the hospital, how she eventually ended up in Canada, how she and the photographer became friends—has been told, briefly, here: http://digitaljournalist.org/issue0008/ng5.htm and at greater length in a book (which I haven't yet read) called The Girl in the Picture by Denise Chong.
Another example, about a different iconic photograph* from a different iconic midcentury event, this one the 1957 integration of Little Rock, Arkansas's high school:
The story (which I have also had occasion to mention before) of the relationship between the two women (girls, at the time) in the photograph has been told by David Margolick, briefly, here: https://www.vanityfair.com/news/2007/09/littlerock200709 and in longer form in his book Elizabeth and Hazel.
But the more I think about it, the more examples come to mind.
There have been many stories told about this famous photograph from V-E day:https://www.artsy.net/article/artsy-editorial-controversy-surrounding-alfred-eisenstaedts-iconic-photo-v-j-day-kiss, but this has gotten a lot of coverage.) And yes, that too has been a book, The Kissing Sailor (another I haven't read), which appears to focus on the who-are-they mystery angle.
Then there's this photograph, less historic than the others here, perhaps, but very widely known in the art world, of the artist Marcel Duchamp playing chess (the activity he abandoned art to persue) while at the first retrospective of his work, with a young woman named Eve Babitz who would go on to be a novelist of some note:
And those are just the ones that come readily to mind. I'm sure there are a lot more. Please leave any that occur to you in the footnotes. It would be nice to curate a list!
* Actually, this one wasn't a single photographs; there were two or three images taken at almost the exact same moment, from different angles, two (at least) of which are widely reprinted; see Margolick for details.