OS X Mountain Lion has a hidden folder full of beautiful wallpapers. If you would like to use any of them, first open Finder press Cmd + Shift + G to bring up the “Go to folder” dialog box.
Copy the next line below then paste it into the Go to the folder dialog box as above.
/System/Library/Frameworks/ScreenSaver.Framework/Versions/A/Resources/Default Collections/
Press Enter or ‘Click’ Go. There are over 40 beautiful wallpapers in these folders for you to use.