This plugin will remove all avatars (and optionally, all icons) from a Buddypress site
Make sure WPMU and BuddyPress are installed and active.
Copy the plugin folder buddypress-remove-avatars/ into /wp-content/plugins/
Browse to the plugin administration screen and activate the plugin.
Please don't hesitate to contact me, especially if you run into trouble. I will respond promptly. email@example.com