Say I wanted to use a painting from the public domain for a book cover. Is it necessary to apply any sort of "public domain mark"? If so, does it need to appear in a particular place (e.g., the cover itself vs. a copyright page)?
The reason I'm attempting to do so is because commons.wikimedia.org has stated that one 'must also include a United States public domain tag to indicate why this work is in the public domain in the United States.'