Although it is not entirely different from the Windows or Mac OS X user interface, the Ubuntu user interface can be intimidating to new users. Changing the desktop wallpaper in Ubuntu 14.10 Utopic Unicorn is not a difficult task if you know where you find the settings. You can select one of the native wallpapers or use your own custom wallpaper. Furthermore, you can use a gradient as wallpaper. If you have two monitors, you can span the wallpaper across both of them.
Click the "System Settings" icon in the Launcher to display the System Settings window.
Click "Appearance" in the Personal section to view all settings related to the look of the desktop.
Select a different wallpaper from the Wallpapers list on the Look tab if you want to use one of the native wallpapers.
Select "Pictures Folder" instead of Wallpapers to use a custom wallpaper and then click the "+" button.
Select the image from the Pictures folder and click "Open" to use it. You can select a different folder from the left pane if you stored the wallpaper elsewhere on the hard drive. You can use any JPG, PNG or GIF image as wallpaper.
Select "Colors and Gradients" instead of "Pictures Folder" to use a gradient, and then select one of the available gradients from the list. Change the gradient colors by clicking each of the colors and picking different colors from the list.