Wally is a Qt4 wallpaper changer using multiple sources like files, folders, FTP remote folders, Flickr, Yahoo!, Panoramio, Pikeo, Ipernity, Photobucket, Buzznet, Picasa and Smugmug images. It is available in many languages. Supported Linux window managers are GNOME, KDE 3, KDE 4, Xfce 4, BlackBox, FluxBox, Window Maker, and FVWM.
Wally wallpaper changer is available in Ubuntu Software Center, but it might be old. The latest stable rpm, deb, macOS packages can be downloaded from http://www.becrux.com/index.php?page=projects&name=wally