Hadn't thought about it before since i don't have a need for them, but yeah i think that could work with swaylock, cause i'm pretty sure you can configure it in such a way that the static indicator isn't on the screen the whole time. I don't know if it can do video files, but you might be able to use a gif instead. Only downside would be that you still have to enter your password to get rid of it again, which isn't typical for a screensaver i think.