The plugin comes with a self-restriction to X-HTML and CSS. Therefore any kind of navigation would mean to reload the page. A possibility but not really an elegant one. I'm not sure if I will do this.
If you need this feature for your project, maybe you want to have a look at my other gallery plugin, the "Very Simple Image Gallery" (usually to be found one or two above or below this extension in the same category), it offers the feature to split galleries to sets of arbitrary size and navigate between them. Should solve your problem. :)