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!!
Muzei - Muzei is a live wallpaper that gently refreshes your home screen each day with famous works of art.
AutoWallpaper - Using AutoWallpaper:
Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
Kuvva - Kuvva is the source for beautiful wallpapers.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads