I think it would be nice if you could make people's webcams an "overlay" (like a twitch extension) over the stream that the viewer can adjust. Features would include Adjusting size, moving location, adjusting transparency, or even turning it on/off.
Often times in streams there is no good place to put a webcam. Sometimes those sections being blocked are important if even for a brief moment. Allowing viewers to cover what they think less important at the time would make viewing much more enjoyable.