I like the increase in avatar size 
I feel for balance sake, the channels could stand to increase along with the avatar.
An issue that will arise though is having lots of “chubby” filled in chat icons that do not differ in view as DMs do.
IE. This looks fine:
But this looks repetitive:
This brings me to another issue that I think possibly could make things better, but is beyond a design experiment (i think).
Could we allow emoji choice as avatars for chat channels? Rather than this default chat icon? Or an icon that is more lightweight? Slack and Discord both have the hashtag as their chat icon which is much more lightweight than our filled in chat bubble icon.