I’m always surprised about just how much great art is now available under the public domain, meaning you can use it for free however you see fit. Artvee is an open source archive of over 100,000 public domain works, including illustrations, photos, drawings and paintings. Download art for free in high resolution.
Browse and download high-resolution, public domain paintings, posters and illustrations.
Travel Between The Pages 
At least this artists chose to leave their art for free. The downside is that corporate business is also leaching on it (ex. Banksy’s dispute with with Full Colour Black) and that many people are so much used to freebies that they don’t have any qualms to download also copyrighted art and literature “for free”.