X11 controlling root window or setting a window to be the background window (wallpaper)

I would like an animated background image. Or better, to make an application be the background, with no interactivity, so I don't accidentally click on it. I've seen many discussions about setting images as background, but is there a way to set an arbitrary application as the background window? I've found this Gifsice snippet on the Arch BBS: gifsicle --animate --new-window root someAnimatedGif.gif but it just opened a regular window (I'm using i3 with LightDM on Arch). I've tried executing it when i3 starts (same result as running it from xterm) and putting it in .Xinitrc, which produced nothing. How/where should I run gifview and is it possible to use another application, such as VLC, as the background window and why does gifview --new-window root not change the root?