In the Vector template the detail page is created with:
https://github.com/arsava/dokuwiki-template-vector/blob/master/inc_detail.php
You can extend it by adding your own custom stuff, or you can modify it via the image metadata handling of DokuWiki.
The image metadata is stored in the images.
Which properties are shown and available in the metadata editor can be modified as explained at
https://www.dokuwiki.org/exif
The metadata editor is in one of the tabs in the third column of the media manager:
https://www.dokuwiki.org/fullscreen_mediamanager
More about the properties:
https://www.dokuwiki.org/devel:templates:detail.php