Rick, I have a sugguestion! Apply a weight field to the user groups, then if they overlap it'll take whichever has a higher weight for the icon...
Admin's would always be #1, Mods #2, then the admin could assign weights for 3+ to other fields...
Good idea - but why not just show a drop down with images available to the user - therefore he could choose whichever icon he wishes and flick between them as he desired.
As long as users can still tell as to who the admins and mods are if they choose another group icon that they belong to - then it should work fine
at the moment - but expanding all the time....) 
