User pictures
From MoodleDocs
Site admins may view the profile pictures of all users on their site using the URL http://www.yourmoodlesite.org/userpix/. The link is only accessible to logged-in admins.
Moodle.org has a modified user pictures URL - http://moodle.org/userpics/ - which shows the profile pictures of the 150 most recent logged-in users.
Users can update their picture by editing their user profile.
The Moodle standard default user picture is . The site administrator can change the default picture.