Filter: postie_place_media

This filter is called before the palceholder (#img1#) is replaced with html markup.

• $html – the html fragment that will replace the placeholder. This html is based on the template specified in the settings for the file type.
• $media_id –  the ID of the media (image) being used to replace the placeholder.

add_filter('postie_place_media', 'my_postie_place_media', 10, 2);

function my_postie_place_media($html, $media_id) {
    return $html . '<p>This image is copyright by me</p>';
}