At our business, we run an opt-in mailing list; when Gmail users open our emails, they see the default "anonymous blue person" icon next to our name. I'd like our logo to appear there.
We already have a G+ page, created using my personal Google account, and a logo is set there, but Google doesn't know of any connection between the G+ page and the business email address.
If our mailing list were a natural person, I think I could create a Google+ account for our list and set a photo there, but it's not a person, so I can't create a G+ account for it. (Google seems to really crack down on that.)