NGA Images. Here you can find over 20,000 high-resolution open access images from the NGA collection. These images depict works that the NGA believes to be in the public domain, and are available free of charge for any commercial or non-commercial use. There is no need to seek permission before using these images.
"As the Gallery marks its 71st anniversary, it is fitting
that we introduce NGA Images and an accompanying open access policy, which
underscore the Gallery's mission and national role in making its collection images and information
available to scholars, educators, and the general public," said Earl A. Powell
III, director, National Gallery of Art. "In turn this supports research,
teaching, and personal enrichment; promotes interdisciplinary research; and
nurtures an appreciation of all that inspires great works of art."
This is good news for scholars, and represents the continuation of a welcome trend in museums to make public domain images freely
See the NGA press release here.