John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Hitomi Downloader - Desktop application to download images/videos/music/text from Hitomi.la and other sites, and more.
Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
HakuNeko - HakuNeko is an all-in-one cross-platform utility that supports you to download manga and anime with various website support.
Wallpaper Cycler - NuonSoft WallpaperCycler is a powerfull utility to manage all your wallpapers and to automatically cycle between your wallpapers.
HDoujin Downloader - A powerful doujin/manga downloader that supports hundreds of different websites.