Variety Wallpaper Changer - Variety is a wallpaper changer for Ubuntu which is featureful, yet slim and very easy to use.
DisplayFusion - DisplayFusion will make your multi-monitor life much easier.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Ultramon - UltraMon is a piece of software built to help with the management of multiple screens on the same computer system. Without software like this, taking full advantage of an expanded desktop space can be difficult.
Wallpaper Engine - Wallpaper Engine enables you to use live wallpapers on your Windows desktop.
Actual Multiple Monitors - Actual Multiple Monitors is a software utility which offers the comprehensive solution to improve the functionality of Windows user interface for comfortable and effective work with multi-monitor configurations.