As many readers already know, a wonderful photo resource for Maya archaeology and epigraphy is Harvard University’s Visual Information Access archive. It contains readable scans of field photos from various projects overseen by the Carnegie Institution of Washington from the 20s through the 50s (Uaxactun, Chichen Itza, Copan, etc.). Just enter a site name in the search engine and you’ll see lots of unsorted images, including many unpublished gems.
http://via.harvard.edu:9080/via/deliver/advancedsearch?_collection=via