For now, you could ask about them on G2G. :-P
You could also create "Free Space" profiles for the photos, like Fred suggested. If any of them are from the same album or were handed down to you by the same person, group those photos on one profile and link to them on an appropriate person's profile. You could create a ==Photo Album== section in the biography, add the link and write something like "Jenny Smith left her mother Betty Jones's 1910's photo album to her daughter. Most of the photos were taken in Kalamazoo, Michigan, but some say Detroit 1913 on the corner. Not every person in the photos is known, but those known include Jim Smith, Bob Smith, and Patsy Jones." By linking to it on the profile, you are giving anyone who is looking for that ancestor an easy way to see the photos. By adding as much information as you can, people who are doing research through Google for things like "Kalamazoo families 1910" or "Jones family pictures Michigan" will have a better chance of finding your photos and possibly identifying some of the unknowns.
I like the idea of a most wanted, but the big problem would be the volume of photos. New posts would bury old posts before the person in the photo was found, making it more difficult for people to see the picture and identify it. If you know where the pictures came from or where they were taken, your best bet may be to contact a local genealogical society and ask if they have a blog they would be willing to post the pictures on. If they come from a small town, you may also have luck with a historical museum or the local archives, too.