You can override the user profile image file path loaded via user->iconURL()

<?php
function my_component_init(){
		ossn_add_hook('profile', 'load:picture', 'my_component_hook');	
}
function my_component_hook($hook, $type, $path, $vars){
		//$vars['user'] contains user instance (OssnUser)
		//$vars['size'] (small, larger, large, etc)
		return 'your new path';
}
ossn_register_callback('ossn', 'init', 'my_component_init');