It would be nice to have a plugin that add gravatar images or other images from a specific location for the users.

For gravatars: you compute the email address from username + email domain from the hudson configuration

For linking images from another server the hudson admin will be supposed to configure only an URL were USERNAME will be replaced with the username. Something like http://pics.example.com/employees/USERNAME.jpg

This feature will provide an easy solution for adding pictures to the users, both solution will not require users to upload a picture.