Setting a background video or image
Background images can be set under 
Menu > Theme > Background > Image > URL.
Images need to be hosted somewhere online. Uploading to Imgur or GitHub are good options to host files.
Add more than one URL separated by spaces or on new lines for a random background image on load.
Unsplash is a great place to find background images. For example, for random images use this URL:
https://source.unsplash.com/random/1920x1080/?night,day,sky
Change the parameters after .../random/ for more Unsplash options.
Loading times may vary depending on your connection or server load.
Background videos can be set under Menu > Theme > Background > Video > URL.
A link to a YouTube page CAN NOT be used as a background video.
Videos should be hosted somewhere online. Simply enter the URL pointing to the video file, e.g. https://github.com/zombieFox/nightTabAssets/blob/main/videos/1626342620002.mp4?raw=true.
Video background only supports MP4 and WebM formats.