Although Windows 7 doesn't support GIF backgrounds such as Windows 10. To set a Thanksgiving animated gif as your wallpaper for Windows 7, you need to create an image folder first. After that, you need to move all the images that you need to use as your animated background. Then you need to right-click on the desktop. And you need to choose the customize option. Now you need to tap on the desktop background that is available in the bottom left corner. Now you need to tap on the browse option. Then choose the thanksgiving image that you need to use. Now, click on the ok option. And you're done.