customized post icons only for new thread OR only for admin
 

On my forums I have customized 30 x 30 post icons for all new threads (which only admin can post, members can only reply), but I would like to disable this for replies or to restrict the use of them to admin only.

Here's an old hack I found which is doing restricting post icons to new threads only:

http://www.vbulletin.org/forum/showthread.php?t=88728


Any ideas?

Thanks in advance.