With millions of images dating back more than 100 years, AP images is one of the world’s largest collections of historical and contemporary imagery. The AP images collection is updated every minute of the day
ARTstor is a digital library of nearly one million images in the areas of art, architecture, the humanities, and social sciences. http://library.artstor.org/#/
CAMIO Catalog of Art Museum Images Online
From antiquity to the present, CAMIO includes photographs, paintings, sculpture, decorative and utilitarian objects, prints, drawings and watercolors, jewelry and costumes, textiles, books, installations, and architecture - plus audio-video and mixed media.