VCard attributes are generated from this utility. Interface can be found at collective.listusers.interfaces.IMapUserAttributesToVCardUtility and default implementation at collective.listusers.browser.vcard.MapUserAttributesToVCardUtility.
To override, create overrides.zcml and configure your own utility providing the interface.
In control panel, administrator can provide a vocabulary as base for a user attribute filter widget.
By default the view is registered at /listusers. If you don’t like that: