There’s a new substantial source of CC0 images, Collections at the Musee de Bretagne (Museum of Brittany, northern France). A test search for “Paris” pictures with images and under CC0 gave 1,298 results. Downloads were initiated by a simple mouse-click, with no hoops to jump through.
In the first tests, image size results were variable, with some being low-res and fuzzy and others being crisp medium-res 3Mb images. Obviously searches will require a passing knowledge of French, as there appears to be no English language interface or tagging. Thus a search for “cat” needs one to know that “chat” is the French word for a cat, and that chromolithograph is “chromolithographie”. Changing the search term from “Paris” to “chat” demonstrated that the site’s search filters/facets are retained across searches. Loading and download speeds are excellent.
A search of the site via Google Images returned no CC results at all, for site:www.collections.musee-bretagne.fr/ “Paris” — under any CC licence. This suggests that Google may be having problems detecting the licences. Google does however offer a useful 2Mb size filter.