In MLA style, if your source doesn't have a specific piece of the citation (like an author's name), you can skip that piece.
For photos that don't have a title, you can use a caption or provide a brief description of the photo. If you write your own description, do not put it in quotation marks.
All citation elements present (author, date, image title):
Creator of image. “Title of Image.” Website Title, date, URL. Medium if not obvious from the image title.