Need a little help displaying rank image for admin only

[Castel]

I want an extra rank image added for admins as part of the galaga shiled ranking hack. I thought it would be simple enough for my limited PHP knowledge but I got stuck anyway.

Here is what I have in showthread.php

PHP Code:

if ($bbuserinfo['usergroupid']==6) {
$rank = "<img src=\"images/ranks/admin.gif\" border=0>";
} else {
$rank = "";
} 


It displays the extra image for everybody. I have tinkered with it for a while now and I either get no image or an image for everybody. What am I doing wrong here?

Thanks