LEWIS WALPOLE LIBRARY (YALE)
The Lewis Walpole Library’s collections include important holdings of 18th-century British prints, drawings, manuscripts, rare books, paintings, and decorative arts. Visit the search page for images.
Quote from their webpage: “Permission to Publish. Provision of a photoduplicate is not an authorization to publish. The Library cannot grant or deny permission to publish texts or images unless Yale University is identified as the copyright holder. If the text or image in question is under copyright, permission to publish should be sought from the owners of the rights, typically the creator or the heirs to his or her estate. The Lewis Walpole Library should, however, be cited as the source with the following credit line: Courtesy of The Lewis Walpole Library, Yale University.”
The helpful people at Yale have compiled a list of other sources for British 18th-century caricature and satire.