Wallch is an application that can be used to change your Ubuntu (Ubuntu derivatives) desktop wallpapers automatically at a particular period of time. It supports Gnome and Unity. It also let you to stop/start wallch, change to next/previous wallpaper. You can adjust/change the wallpaper changing interval. Wallch supports live Earth wallpapers which updates automatically every half an hour, therefore you can set the live Earth wallpapers as your desktop background.
Install Wallch On Ubuntu
For Ubuntu 12.04 or below versions, add the following PPA.
$ sudo add-apt-repository ppa:wallch/version-3-ppa
Update Sources list.
$ sudo apt-get update
Now install Wallch using the following command.
$ sudo apt-get install wallch
Wallch is available in Ubuntu 13.04 official repositories. So you don’t have to add any external repositories. Just run the command sudo apt-get install wallch to install it.
Launch Wallch
Open it up either from Dash or Menu. Wallch will look like below.
To add images to Wallch, click on the Add or Add folder and select the folder that contains images. Check the boxes “Change Wallpaper choosing images randomly”and “Change Wallpaper in random time”.
Finally click on Start. Now Wallch will change wallpapers automatically in random time (Default time is 10 minutes). Also Wallch has Unity integration (unity launcher) that allows you to stop/start Wallch or Change to next/previous wallpapers as well.
Wallch has a feature called Picture of the day from Wikipedia. If you want to activate Live Earth Aallpaper or Picture of the day from Wikipedia, just stop the regular wallpaper changer and goto Edit -> Extras. Click on Activate Live Earth Wallpaper or Picture Of The Day.
It also has feature called Monitor Folder which means that any images added to or removed from the monitored folder, will automatically be added to or removed from the list of selected wallpapers. If you stop monitoring this folder all the images from it will be removed from the list of selected wallpapers.
It also has other cool features such as Desktop/Sound notification, Log history, taking screenshot of any screens, taking images from webcam etc.
 desktop wallpapers automatically at a particular period of time.){kind=link}