Upgrading ezimage attributes from the eZ Publish 3.2 branch to the 3.3 image system is done on the fly (when the ezimage attribute's content is accessed). So there might be 3.2 items remaining if they weren't accessed after update.

To be able to drop some old db tables and PHP classes (ezimage, ezimagevariation) we will need a script that ensures all old image data is converted to the system introduced in 3.3.

See eZImageAliasHandler::generateXMLData().