This falls under graphic design for sure. Many people opt to find free Twitch Overlays or premade ones that are super cheap to use on their streams. The overlays can tell you your latest follower, subscriber, donation and much more. They also visually represent the streamer in some way by way of panels and logos. Do you prefer to watch streams with or without overlays and why?
I stream everyday from 7PM UK Time till 10pm and I always have overlays. I don't go over the top with it as it's very very important that your viewers see more of the game then anything else. The overlay I have is from Three free different packs that I edited and put three together till I liked it and fit my needs.
Time, Date, year
Stream account name
Latest Donation & follow
social media account details
See allot of streamers that don't even have overlays apart from there webcam.