Oh boy, another email server thread. Queue the pitchforks against Google's monopolistic behaviour against even well managed domains.
I did a not-for-public writeup on BIMI recently. It boggles my mind that there are no widely used ID services (that is, avatar management and name consistency), especially for something as fundamental as email.
Turns out, you can absolutely setup a BIMI record without paying the ludicrous $1500 cert fee. Turns out, Yahoo and AOL even show those images to senders (at least when I tested last year).
Turns out, Google marks you as spam on an otherwise passing email setup (full alignment, policy = reject all, etc) when you do that. >:(