I have changed avatar specification of PQA (Q2A).
Admin (users) options:
Specification is same with WordPress. Please refer details in Gravatar image request rules.
If you have enabled Gravatar, users can not select "none". Users who have not registered avatar to Gravatar will show default Gravatar. If you select "Identicon"/ "MonsterID"/ "Wavatar"/ "Retro" in admin panel, user avatar is generated automatically. Therefore, users do not need to register own avatar. And, if you checked "Force Gravatar default", default avatar will be displayed forcibly for users who have already have Gravatar.
Example of this site:
- Gravatar maximum Rating: "g"
- Default Gravatar: Identicon
- Force Gravatar default: ON