Maybe a decent way to start would be to go look at what existing stream sites are putting out for content and see what you liked and disliked from the existing offerings?
Like from the get-go it seems kind of obvious to me that you would not want any kind of gaming related stream content but maybe that's not true?
I think that stuff like this is a great way of trying to figure out how to digitize real-world relationships like the economies that form at Burning Man type of events.
A friend of mine has just sent me an invitation to a online music festival that's supposed to be going on until the 10th. Theres a lot of exploration going on in the realm of distance socializing.