Wish list in order;
EXIF in database
Tags (categories can be emulated by tags, and in the end tags are more powerful)
Create more users
Announcements in admin area
Since it's aimed at photo's it seems obvious to have the EXIF data available to show, search and organise.
I think the admin area (maybe the first screen?) you could have a area like on WP that keeps you updated on the Zenphoto news? This would be really handy during the dev to get news on plans and releases?