Hello Erhard,
It seems like, some image fields are not implemented in the new UI, yet.
Image field is one of them - in the new UI it just renders as a text field.
If you switch to the legacy view mode, it’s working just as it used to in 7.
(at least that’s what I assume - if you add an image to the documents e. g. for testing, it works).
You can try and switch your contacts to the compatibility mode: