I've been emailing today with photographers who use Flickr to manage their sets and collections. They like it that people can view their pictures publicly, but they want to control how they're used. RSS, used as a way to distribute pictures, is a new idea for many of them.
Based on these conversations I think it's important that they have a way to:
1. Turn off the RSS feed for their pictures.
2. To have their pictures not included in RSS feeds based on tags and searches.
3. To include their pictures in RSS feeds, but only links to them, and the titles and descriptions, but not as enclosures.
Of course this recommendation isn't just for Flickr, it's a good idea for any photo-sharing site.