It would be nice to be able to mark something as private, but still allow people to view it if they are given a link.
Additionally (and that is less likely to happen as it brings a lot of complication) - it would be nice, especially with already some level of "trust" between you guys and facebook, to share a single image from a private story, without a need to make it public... or ability for user to look at the rest of the story.
Another option would be to allow private images to be "exported" or "linekd" to a "semi-public" folder that would only allow a logged in owner to view them all, but would allow access to a single image through the link shared by the user - that one would allow both - facebook or otherwise sharing, while not allowing unauthorized people to that through them....
Sorry - just brainstorming here ;) It all came to be after sharing some LYTRO pics involving a gun, and the family getting up in arms... By making it private I am not even able to show it to the person on the picture till we visit him the next time... So I am just thinking of "tricks" to resolve such issues in the future. Some ideas are sort of "rooted" in using Picasa, since I heavily use that to share images with fam over the pond.