I’d love if it worked like LINE, where you can set different backgrounds for yourself without forcing them on the other person. I use that feature a lot to differentiate the different chats.
Ideally they could have a toggle when choosing a background that makes it shared or not, so that if it’s shared it shows it to the other person, but either side could then turn the shared background off for themselves and have their own background locally. The best of both worlds! The existing option in Settings could still be there to turn it off completely across all chats.