License, verbatimPD
The National Gallery of Art: open access image with no usage restrictions under the NGA's open access policy (openaccess=1 in the Gallery's published_images dataset).
Francisco Goya. Palenque de los moros hecho con burros para defenderse del toro embolado (The Moors Use Donkeys as a Barrier to Defend Themselves against the Bull Whose Horns have been Tipped with Balls), in or before 1816. National Gallery of Art, Washington.