Many libraries will keep the personal items to return to the patron but few patrons do return them. So if you've used a photograph for a bookmark and have since lost it, you may want to check with the library's lost and found.
Libraries are having two issues. First, patrons aren't returning books. Second, when the books are returned, they often come with a variety of junk inside them. An Arizona librarian reports everything from cash to toilet paper to muscle relaxants to a check for $10,000.00.