Article: Enable hidden retina sized wallpapers in Mountain Lion
There are 3200x2000 pixel wallpapers hidden in the depths of OS X. These 43 "retina-sized" images only show by default on Apple's latest Retina MacBook Pros. However, you can access them on any machine running OS X. The secret cache of pics is located in a default system folder named ScreenSaver.framework. Here's how to get to it.
The files are located in /System/Library/Frameworks/ScreenSaver.Framework/Versions/A/Resources/Default Collections/. Navigate to them in Finder as shown above to expose the full sized jpg images.
To add them to your default wallpaper or screensaver, add the folders through System Preferences > Desktop & Screen Saver. There are four different folders, National Geographic, Aerial, Cosmos, and Nature Patterns.
Wow! I was looking for more stock wallpapers for my 27" 1440p Achieva Shimian monitor, and my wish has been granted! Thanks! Cosmos07.jpg looks fantastic even though the resolution of the monitor is less than the pic!