To transform your picture gallery in a pretty slideshow just add this code wherever in the templates of your product closeup:

<SCRIPT type="text/javascript">$(document).ready(function(){ $('#galleryslide').cycle(); });</SCRIPT>
<div id="galleryslide">
<%FOREACH item IN product.gallery >
  <IMG class="display" width="240" height="180" SRC="%-item.content-%">
</%FOREACH>
</div>

Please note your page will require the library "Jquery Cycle plugin", if it's not already included in your theme, please download it from http://malsup.com/jquery/cycle/