I had the same thought and did some research. The list of pictures deemed “interesting” are actually generated by Flickr. The “Flickr Gallery” plugin just pulls those photos from Flickr.
The degree of “interestingness” is determined by an algorithm used by Flickr, and is not public information (discussion on that topic here: http://www.flickr.com/help/forum/en-us/10748/#reply53048)
To see your interesting photos on Flickr, go to Flickr.com, Photostream, Popular (tab at the top of the photostream), and there your interesting photos are displayed.
