Kodi - Kodi is an award winning free and open source media player that got its start on the Xbox console.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Universal Media Server - Universal Media Server allows you to host your entire library of video, music, and pictures, and broadcast them conveniently to a wide variety of different devices.
Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
Emby - media server for personal streaming movies tv music photos in mobile app or browser for all devices android iOS windows phone appletv androidtv smarttv and dlna.
Muzei - Muzei is a live wallpaper that gently refreshes your home screen each day with famous works of art.