what about adding this code in the plugin...
Code:
if ($vbulletin->userinfo['userid'] > 0 && $vbulletin->userinfo['userid'] != '' || !$vbulletin->userinfo['userid'])
{
require_once(DIR . '/includes/functions_user.php');
$vbulletin->userinfo['avatar_build'] = fetch_avatar_url($vbulletin->userinfo['userid']);
if (empty($vbulletin->userinfo['avatar_build']) || !is_array($vbulletin->userinfo['avatar_build']))
{
$vbulletin->userinfo['avatar_build'] = array('noavatar.gif');
}
$vbulletin->userinfo['avatar_build'] = '<img src="' . $vbulletin->userinfo['avatar_build'][0] . '"'.iif($vbulletin->userinfo['avatar_build'][1],$vbulletin->userinfo['avatar_build'][1],'').'border="0" alt="Edit Your Avatar" />';
Then just make a noavatar image...and turn this into an extension...