I put just the simple word autumn into the search window at Google Art and it returned so many and such wonderful works on that subject that it brought tears to my eyes. Altogether there are more than 600 works and many, many of them are wonderful.
Google Art Project currently has 20 or so paintings by Hans Holbein the Younger on display. Very handsome works. Many of these works are quite wonderful but you might need to zoom in to see just how much. Try the portrait of Jane Seymour, Queen of England and one of Henry VIII's ill-fated wives. Jane was not a terribly attractive woman but the painting, seen up-close, is simply marvelous.
The Google Art Project offers terrific resolution on most of the thousands of works now displayed at its site. There are 164 works, though, that are rendered in 'gigapixels,' the Project's highest level of resolution. Feast your eyes!