AutoWallpaper - Using AutoWallpaper:
DesktopSlides - DesktopSlides is a light and user friendly desktop wallpaper changer for windows.
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!!
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Pixiv for Muzei 3 - Best Pixiv plugin for Muzei 3
AeroWallpaperChanger - AeroWallpaperChanger is another "wallpaper changer" software for Windows 7.