This example loads a gallery. Markup can be done using stylesheets. (styles.css)
The "photosperrow" parameter in the configuration file controls the number of photos per row.
Alternatively you can simply add "&photosperrow=4" to the url of the IFRAME, and it will overrule the configuration!
Same applies to the number of photos it will show per page. Use "&photosperpage=9" (see source of this page) to alter this.

Note that the IFRAME does not automatically resize to the content, so you will have to set the width/height yourself. Use the PHP variant if you want to be more flexible.