Wallpaper changer

HydraPaper is a free and open source wallpaper manager with multi-monitor support

Superpaper is a free and open-source, multi-platform software for automatically changing your desktop wallpaper with support for working with multiple monitors

BingWall – free and open source, utility to browse/download/setting bing’s wallpaper of the day to GNOME desktop

WallpaperDownloader – free and open source, software for downloading, managing and automatically changing wallpapers from the Internet for Linux

Variety – free and open source wallpaper downloader and manager for Linux systems