This would exclude the admin (you) from getting an image and also newly created usergroup that would have a group ID of 8. If you want to give a few people a special status you could move these people in the new user group and edit their profile title from the admin panel. From there you can include html in the title. For example you could put -- General<br><img src=images/ranks/general.gif> -- as the tile for that person. If you have more than one admin (and you want other admins to have the default image) you could change the code above from post[usergroupid] to post[userid] and add your specific ID number
I'm sure there is a better automated way of doing this but that is far beyond my limited PHP knowledge at this point.