Animated GIFs are moving images in compressed form, designed for being displayed on computers and in Web browsers without any special add-ons or plugins. Because they register as "normal" images, like still JPGs or PNGs, they can be used in a variety of places. However, while animated GIFs do have a variety of uses, they cannot be set as your Mac's desktop wallpaper without plenty of tinkering that might not be worth it.
Operating System Capabitilities
Older Windows operating system allow you to set an animated GIF as your desktop background with little trouble. For example, in XP, you can simply select the image when browsing for images. Later versions of Windows allow you to set an image as your wallpaper by installing applications specifically for that purpose. Other systems, such as Mac and Linux, do not have the same native capabilities, and even third-party solutions for these operating systems involve a complex process.
On a Mac, you are limited to using only still images as your desktop background. You can select an animated GIF file, but it will only show one frame of the GIF, and it will not animate. The operating system does not allow it, so this cannot be tweaked using any of Mac's default options and preferences.
Getting around the system's native limitations requires installing software that allows you to set your computer's screensavers as your background, then finding a way to convert your animated GIF to a screensaver format. This can be confusing and take a lot of time, especially if you are a novice computer user.
If you do decide to attempt to set an animated GIF as your desktop wallpaper, be cautious. It takes a lot of processor power to run an animation on your desktop, and the animation will take up a high percentage of your computer's RAM, or Random Access Memory, so if you try to run any other programs while the animation is running, the applications themselves will run slower due to the lack of available RAM. On top of that, if the animation is running all the time, you run the risk of overheating your computer, with its fans running full speed all the time.