AutoWallpaper - Using AutoWallpaper:
Becrux Wally - Wally is a Qt4 wallpaper changer, using multiple sources like files, folders, FTP remote folders, Flickr, Panoramio, Ipernity, Photobucket, Buzznet, Picasa, Smugmug, Google, Vladstudio and deviantART images. Now it's available in many languages!!
Artpip - Artistic wallpaper for your desktop, refreshed daily.
Pixiv for Muzei 3 - Best Pixiv plugin for Muzei 3
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Kuvva - Kuvva is the source for beautiful wallpapers.