A gravatar is an image registered to an e-mail address.
You can submit yours on-line at http://www.gravatar.com.
The following variables offer control over how things are displayed.
The size in pixels of gravatars. Gravatars are always square, so one number for the size is enough.
List of image properties applied to Gravatar images.
Regexp that matches mail addresses or names of people of which avatars
should not be displayed, or
nil. It default to the value of
gnus-article-x-face-too-ugly (see X-Face).
If you want to see them in the From field, set:
(setq gnus-treat-from-gravatar 'head)
If you want to see them in the Cc and To fields, set:
(setq gnus-treat-mail-gravatar 'head)