Desktop pictures, or wallpaper, are one way to make your Mac truly your own. Choosing from one of the beautifully rendered images that are provided along with OS X is one way to be sure to impress any passers-by, as well and give you something beautiful to look at as you go about your daily Mac business.
Now, however, Mountain Lion lets you easily use any of your own images from iPhoto (or Aperture) as a Desktop Picture, right within the Desktop & Screensaver preference pane. Here’s how.
Launch System Preferences from the Applications folder, the Dock, or the Apple menu and click on the Desktop & Screensaver icon to bring up the preference pane. Then, click on the Desktop tab at the top to see all the gorgous imagery Apple’s already provided for you to pretty up your Mac’s screen.
Click on the triangle next to the word Apple at the top, however, and you’ll see a section for iPhoto. You may need to expand the iPhoto section by clicking on the triangle next to it. If you have Aperture installed, you’ll see a section for pictures in that program as well.
Now, click on the left column to select images from your Events, Photos, Faces, Places, Last IMport, Last 12 Months, Photo Stream, Flagged, or from any album you’ve created in iPhoto. The images will show up on the right side, just like the Apple ones do when they are selected in this preference pane. Click on the image you want to use and presto! The chosen image will appear as your Desktop picture.
Now you can use all the photos you’ve taken yourself without having to open iPhoto or Aperture, copy the image over to the Desktop, and then drag into the Desktop pictures preference pane. This simplifies things quite a bit.