I suggested to the folks behind pop.com, which does not show your face to you, to implement some form of indirect feedback mechanism when your face is aligned and centered. I thought maybe a small face+camera icon that turns red/yellow/green depending on whether your face is not visible, sideways/non-centered, or centered and in focus. That way even if you don't see yourself, at least you will know that others can see you fine.

Who are these folks? I have a tonne of suggestions and would love to give feedback!

This should be trivial for the people at zoom to add. They already split the background and foreground in the video for displaying images that aren't the wall/messy room behind you.