Is it possible to use a GIF as my wallpaper? So it has come to my attention that Live Wallpapers are not actually images but more of like, applications that are active in the background. This causes it to be a bit of a battery hog. So I was thinking, if I can just use a GIF instead (like how I did on older Nokia dumbphones), then that would at least decrease the battery usage while still having my wallpaper do some activity.

When trying to set a sample GIF as wallpaper, it is asking me to crop it which I guess, in turn, removes its animation. How do I make it so that a GIF of my choice is used as the wallpaper on my phone while still retaining its animation?
There is no native way to do this, as Android simply does not support it. Any wallpaper which is not a live wallpaper will be displayed as a static image. Specifically, Romain Guy notes in a comment on the Android issue tracker that all regular wallpapers are saved as PNG images after cropping. There is no way to change this behaviour aside from modifying the Android source code.

There are some third-party apps that will allow you to use an animated GIF as a wallpaper, such as AnimGIF Live Wallpaper. The downside, though, is that I believe all of these will be live wallpaper applications, which sort of defeats the purpose.