Upcoming cool Instagram update!
The option is available (to those who can access it) via a new 'Selfie' sticker option, and the rounded, selfie stickers can be applied as many times as you like within a Stories frame.
If it does get a wider release, it would be another creative consideration for your Stories. And it looks impressive - you can imagine that it will prove popular, if, again, it does, in fact, end up getting the green light.