plugins/push_notification/public/style.css
.controller-profile_editor a.control-panel-push-notifications {
background-image: url("/plugins/push_notification/images/control-panel/push-notification-settings.png");
}
.controller-profile_editor .msie6 a.control-panel-push-notifications {
background-image: url("/plugins/push_notification/images/control-panel/push-notification-settings.jpg");
}