Things like swipe up on a vine to view the artist’s page, maybe double tap to like (that’s not copyrighted, is it?? ), tap in the middle of the screen to mute/enable closed captioning, etc. Maybe draw a circle on the screen like and it makes the video auto-repeat or not.
Expanding on the mute/closed captioning thing: there should be an option in settings to auto-enable at least the CCs; but if being given a gesture control, it should be a relatively quick action with a fast response time, 'cause, y’know, these things are only six seconds.
The time that it takes to do a gesturing action should be kept in mind when deciding which feature it should control.
Maybe in settings there could be a custom gesture control page where it lists things like “mute”, “view artist page”, etc. and you could set your own gestures for it.
Add on more ideas below !!