The Yale University Art Gallery opened it collection to the public  and allows images to be downloaded without permission as long as the individual items are in the public domain.  It is not possible to limit the search parameters specifically to images in the public domain.  One must search for the desired image(s), and use the meta-data to determine whether or not the image is in the public domain.  Only images that are in the public domain will give the user the opportunity to download the image.  The Gallery also makes available orphan works for download.  Among the orphan works in the museum’s collection available for download is Edward Hopper’s Western Motel.