You can have every user-uploaded avatar image added to a moderation queue for approval or rejection.
Fastpath: Admin Console: People > Settings > Avatar Settings
> Moderate uploaded user avatars
When you choose to have avatars moderated, a user uploading an avatar will be told by the interface that their avatar choice is pending approval. Once approved, the avatar will be available for the user to designate it (or others) as their primary avatar. It will not become the user's primary avatar until the user manually selects it after moderator approval.
After a user uploads an avatar, the avatar moderation queue becomes available to the
moderator through a link on the Avatar Settings page in the Admin Console as shown in
the following image.
Note: The avatar moderator will see the link only when there are
images in the queue waiting to be moderated.
The moderator will then select for images listed in the avatar moderation queue.
Note: User-uploaded avatars won't appear with the default avatar images on the Avatar
Settings page. You can view (and delete) a user's uploaded avatar by going to their
account summary page in the Admin Console. To do that, click , then click the user's name in the list to view their summary page. On
the bottom of that page, under User Avatars, you can view and delete their uploaded
avatar images.