FamilySearch.org Photos has a "Find" function. I wrote about my efforts to figure out how it worked a short while ago. Each photo can have three different identifying fields; a title, a description and an event. The following screenshot has the title marked as No. 1, the description marked as No. 2, and the Event link marked as No. 3.
The link to the Event field allows two further choices, entering a date and/or a place.
Now, the question was, which, if any, of these fields were searched by using the Find function located in the menu bar at the top of the page in the shaded area below the FamilySearch logo and standard menu items?
The answer to this question is all of them, but only if at least one person in the photograph is tagged to someone in the Family Tree program. Otherwise, none of the fields' contents will be found. The only problem is what if you don't know the person in photo and wanted to allow people to search for a place and try and identify people from a particular place?
So far, I have found no way to do this but to tag the photo to some person in Family Tree. In my case, I elected to tag the person to the individual who took the photographs or accumulated them, that is, my Great-grandmother Margaret Godfrey Jarvis Overson. Do I really want thousands of unknown photos tagged to the wrong person? How else can I upload unidentified individuals and allow other users the opportunity to identify their ancestors? Should I forget the whole idea and simply remove the photos I have already uploaded that were clearly taken by a photographer in St. Johns, Apache, Arizona?
These seem to me to be interesting questions.