I'm wondering if Drupal allows me to attach multiple informations to an multiupload image field. F.e. copyright, creator and taxonomy references for people appearing on the picture. Is there any module that can handle these requirements? If not, where could I hook in?
Although your mileage will vary, what you're looking for is File Entity.
This module will promote files into fully fledged entities, allowing them to have fields in the same way as all other entities (eg nodes). You can then add whatever fields you'd like, from the pool of field modules you have installed.