An administrator is allowed to remove images. They're likely a part of your CB moderator view access level. Login as a normal registered user (no other user groups except Registered) and see if they can remove someone elses image; they should not be able to unless your moderator view access level has Registered selected. If issue persists after performing this test please PM backend super administrator login credentials and will take a look.

Please PM backend super administrator login credentials and will take a look. It sounds like your CB moderator setting is incorrectly allowing everyone to be a moderator.

Have reviewed your install and as originally suggested you have a moderator permissions issue. Your moderator View Access Level within CB > Configuration > Moderation is set to "Super Utilisateur". When you go to Users > View Access Levels and edit "Super Utilisateur" you can see you have nearly all of your usergroups selected. This means all of those usergroups selected have CB Moderator permissions. You need to adjust your "Super Utilisateur" View Access Level as needed. To be specific "Enregistré" is your Registered usergroup and it is selected in the "Super Utilisateur" View Access Level, which means all registered users are CB Moderators.