As you know, with Teams you can chat with peoples, including multiple one at the same (also called group chat), outside of meeting or Teams channel.
By default, and until now, the group chat profile picture was showing a mosaic of the people’s pictures involved in the chat.
Well, good news as you can now customize these group chats using an avatar (built-in, your own picture or emoji).
To customize your group chat profile picture, just click on the current one and select either of the option