Allen Snook

A WordPress plugin that gives users control over whether or not to opt-in to Gravatar. Avoids revealing Gravatars to logged-out visitors.

Profile Picture Privacy Controls

A WordPress plugin that gives users control over whether or not to opt-in to Gravatar. Avoids revealing Gravatars to logged-out visitors.

Podamibe Nepal

This is a plugin that allows users to upload their own gravatar in the media gallery and displays that image as gravatar instead of grabbing avatar from gravatar.com based on their registered email.
You can also use the default gravatar by disabling custom gravatar.

Podamibe Custom User Gravatar

Replace Gravatar with custom picture in your gallery

Profile Picture Privacy Controls vs Podamibe Custom User Gravatar