Lagoon comes with a number of useful resources which you can use. You 
access these resources in the sitemap with res: URLs.
An XSLT stylesheet to generate an HTML index page with thumbnails for a set
of images. It's used in conjunction with the 
<source type="dir"> producer. It requires you to put all 
images in a directory images and thumbnails for them (with the 
same filename as the corresponding image) in a directory 
thumbnails (at the same level as the images directory).
(Lagoon does not generate thumbnails for you.) It needs
two parameters, title for the title of the page and 
rowlen for the number of thumbnails to put on one row.
Example of usage in sitemap:
<file target="/index.html" source="/images/">
  <format type="html">
    <transform type="xslt" stylesheet="res:/style/imageindex.xsl" title="My pictures" rowlen="8"> 
      <source type="dir"/>
    </transform>
  </format>
</file>