Present an untagged photo and ask the user to tag it.
Adds a random thumb ( items with no tags ), as a sidebar block and allows users to tag the item.
This module may be downloaded from the Gallery-modules repository here. Click the appropriate zip file.
To install, extract the "tag_it" folder from the zip/rar file into your Gallery 3 modules folder. Afterward log into your Gallery web site as an administrator and activate the module in the Admin -> Modules menu. Done!
You will be able to reorder the items in the sidebar via Admin -> Appearance -> Manage sidebar.