I see this topic touched on in another post, but it has become of particular interest to me, so perhaps others will weigh in on it.
I, too, work with images and would appreciate the convenience of viewing and embedding metadata into these files, as the comments box just isn’t cutting it for me anymore.
Even more importantly, I have found a need to associate bibliographic data (URL, etc.) to PDFs that I download, and see the possibility of data fields associated with a particular file as becoming more and more important to integrating my entire workflow into DEVONthink.
Since the comment box is sort of messy for entering separate fields of information, I considered trying to integrate a bibliographic manager (EndNotes, BookEnds) with the information I had stored in DEVONthink, but decided it would be too much of a headache and am still entering relevant information into comments for now.
I see similarities the request made for metadata capabilities for images and my desire for user-defined data fields. I don’t know much about databases, but both seem to involve associating additional information with a particular file, perhaps a more refined method of inputting information in the comments box.