After looking at the media-rss.php file, this is what I've found:
The RSS Feed lists pictures in three ways: 10 Last Pictures (default), Gallery and Album. As far as I can tell, there is no way to choose any of these options from within NextGen Settings. Please correct me if I'm wrong.
Can you please add the ability to choose which setting you want displayed as well as a selection for the gallery/album or how many of the last pictures if appropriate?
Also, It would be nice to have the option to display "all" or "random order".