Thanks for the fast response, Melissa.
I was looking for a way to use a video from my media library as the background, but the builder wasn’t displaying it when I chose a video instead of an image because I was mistakenly using a slider.
Now I’m trying to use the bgvideo plugin, but it sets the video’s z-index to -1, and the page divs completely cover the video if it’s smaller than 0. I’ll keep investigating.