You need a notification view hook to specify template for viewing your notification type item in notification list.

A working example can be found on https://www.opensource-socialnetwork.org/component/view/5526/notification-sample
~~~
<?php
function my_component_init(){
//example for type `notification:message:tomyself`
ossn_add_hook('notification:view', 'notification:message:tomyself', 'notification_sample_myself_view');

}
function notification_sample_myself_view($hook, $type, $return, $params){
$notif = $params;
$user = ossn_user_by_guid($notif->poster_guid);
$url = ossn_site_url("u/".$user->username);
$iconURL = $user->iconURL()->small;
return ossn_plugin_view('notifications/template/view', array(
'iconURL' => $iconURL,
'guid' => $notif->guid,
'type' => 'notification:message:tomyself',
'viewed' => $notif->viewed,
'url' => $url,
'icon_type' => 'alert',
'fullname' => $user->fullname,
));
}
ossn_register_callback('ossn', 'init', 'my_component_init');
~~~