If more than one chatter has a chat picture that is obviously from the same picture, either chatter has the right to contact the graphics department (firstname.lastname@example.org) about the duplicate icon. In the email, the chatter complaining of the duplicate must include both their nickname, the nickname of the other party involved, and a description of the icon. Within one week, the graphics department will look at each account. The person who uploaded the icon in question first will be allowed to keep it, and the other person will have their icon taken offline-- even if they were the person who brought the duplicate icon to the attention of the graphics department. When an icon is taken offline, it will remain in the person's account until they delete it, and the person will be paged with the name of the icon taken offline, and the reason it was taken offline.
You acknowledge that we do not go through accounts looking for duplicates. The only duplicate matters that are reviewed are ones that are brought to our attention. If a person does not bring a duplicate matter to the attention of the graphics department, it will be assumed that the creator of the original icon has given permission to others to use it.