You can improve your visitors’ privacy and your websites performance, by serving avatars from your own domain instead of pulling them from gravatar.com. Avatar Privacy enables users to upload their own avatar, use a generated one, or consent to the usage of gravatars.
Extract from WordPress.org
Avatars from Gravatar.com are great, but they come with certain privacy implications. You as site admin may already know this, but your visitors and users probably don’t. Avatar Privacy can help to improve the privacy situation by making some subtle changes to the way avatars are displayed on your site.https://wordpress.org/plugins/avatar-privacy/