Hi Deanna, William P Pinkham was a Friends minister born 3 Sep 1841 in Litchfield, ME and married Emma Cecelia Curry 27 Sep 1860 in Salem, OH. The only possibly living descendant I know of would be a Wendell Pinkham Dixon born 22 July 1906 and is not listed in SSDI yet. You might be able to find him with search engine people finders?? If you are unable to locate family, you could donate the photos to the PFHS Archive. At least you now know who they are and I'd be glad to supply ancestry if anyone's interested.
Pinkham Family History Society 1867 Bedford Road Columbus, OH 43212