First, Zenphoto is a real CMS as it manages content..;-)
Quote:It seems that ZenPhoto's sitemap feature includes links to the images (as albums actually, which is interesting.)
I don't understand this. Zenphoto's sitemap plugin generates several sub sitemap files for images and albums and possible Zenpage items. A sitemap is a list of links so a search engine can find them more easily. Google itself has some info about that.
There is no guarantee that it will index everything. This is a quite complicated matter what Google thinks is important to be listed where. The best is always to have content real people are interested in so they refer to your site.
There is a whole SEO/SEM industry trying to figure that out whenever Google changes something. We really cannot provide this services here.
If you are concerned about that you should open a Google Webmaster account and let that tell you a few more details about your site in Google's index. All also depends of course on the theme used and how that is setup, valid html, Js stuff hiding something etc.
If you are on an older Zenphoto release you should try the 1.4.3 beta as the sitemap plugin has some bug fixes in there (if I recall right)
(I hope you are not talking about the site linked in your profile as that does not use Zenphoto at all. just asking....)