Change the desktop background
You can change the image used for your desktop background, or set it to a simple color or gradient.
Right click on the desktop and select Change Desktop Background.
Select an image or color. The settings are applied immediately.to view your entire desktop.
There are three choices in the drop-down list on the top right.
Select Wallpapers to use one of the many professional background images that ship with Ubuntu. With the exception of the Ubuntu wallpaper, all of the default wallpaper choices were created by winners of a Community Wallpaper Contest.
Some wallpapers are partially transparent and allow a background color to show through. For these wallpapers, there will be a color selector button in the bottom-right corner.
Select Pictures Folder to use one of your own photos from your Pictures folder. Most photo management applications store photos there.
Select Colors & Gradients to just use a flat color or a linear gradient. Color selector buttons will appear in the bottom right corner.
You can also browse for any picture on your computer by clicking the + button. Any picture you add this way will show up under Pictures Folder. You can remove it from the list by selecting it and clicking the - button. Removing a picture from the list will not delete the original file.