Upload and view the photo in the same interface

Currently there is no supported way of doing that. Files are in a temporary state until the form is submitted.

Stefan is correct, however the easy workaround to this is just to make the user submit the form via some extra click (link, button, etc, perhaps labelled "click here to preview"); the process flow would chain the user directly back to the same form again and in the user's experience it'll seem as if they never left.  It just requires the extra click which there's no current way to avoid.