The paintings behind the homepage frames are public-domain works from the Art Institute of Chicago, released under CC0.
Nocturne: Blue and Gold—Southampton Water
James McNeill Whistler, 1872
Stacks of Wheat (Sunset, Snow Effect)
Claude Monet, 1890–91
Water Lilies
Claude Monet, 1906
The Home of the Heron
George Inness, 1893
Early Morning, Tarpon Springs
George Inness, 1892