Hi inhouse,
Great question!
Additional fields are supported for events but, currently, not for venues or organizers. That said, if you’re at home developing for the WordPress platform I don’t see why they couldn’t be added in with a small customization. Beyond that I’d suggest posting a feature request for this over on our UserVoice page.
Positioning extra fields within the meta area (where organizer and venue details etc are displayed on the single event pages) is something of an advanced customization at this time: we do have some information about this in our tutorials section that you may wish to review though: How the Meta Factory Works.
I hope that helps – and please do post a feature request (or add your support to any suitable existing request).
Thanks!