Browsable catalog of the collection of the Library of Congress. While much of the material has fallen into public domain and can be freely used, it is important to read the 'Rights Advisory' for any image you plan to use, and do your research if the copyright status is in doubt.
Browsable catalog of the collection of the Portland Art Museum. Collections include: African Art, American Art, Ancient Art, Asian Art, European Art, Graphic Arts, Modern & Contemporary Art, Native American Art, Northwest Art, Photography, Pre-Columbian Art, and Western Decorative Art.
The British Library’s collections on Flickr Commons offer access to millions of public domain images, which we encourage you to explore and re-use. The release of these collections into the public domain represent the Library's desire to improve knowledge of and about them, to enable novel and unexpected ways of using them, and to begin working with researchers to explore and interpret large scale digital collections.