NYPL Digital Gallery

The New York Public Library Digital Gallery provides access to over 415,000 images digitized from primary sources and printed rarities in the collections of The New York Public Library, including illuminated manuscripts, historical maps, vintage posters, rare prints and photographs, illustrated books, printed ephemera, and more.
This is a free service offering digital images of historical materials from the Research Libraries' original, rare and specialized holdings. NYPL provides free and open access to its Digital Gallery and images may be freely downloaded for personal, research and study purposes only.

Obviously American but might be worth a look.