An open access photography archive of British art and architecture collected by the Paul Mellon Centre from 1964 is now available to browse online. It consists of photographs of works that were often behind closed doors of private houses and collections, and has a particular emphasis on 18th century art.
This historically important and visually rich collection has now been digitised, with typed and handwritten descriptive notations transcribed for searchability, and is available, free, online.
Many images are available for re-use through Creative Commons licenses, but please check before using any images in this way.

Two Carib Women, A Child Holding The Hand Of One by Augustus Brunai from the Paul Mellon Photography Archive (image in the public domain CC0 1.0)
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