I was using your product today. I found it very interesting . However I have noticed the images and videos added dynamically to the div tag hosting the plugin do not get rendered. The div tag shows blank.
You can view this tutorial: http://html5box.com/html5gallery/initialize.php
The idea is, do not add the class name html5gallery to the div, use an id instead. Like following:
<div id="mygallery1" data-skin="gallery" data-width="480" data-height="270" style="display:none;"></div>