[Zope] Image as a Property of a ZClass

[Nathan Clark]

I have created a ZClass, "BookReview", as a subclass of ZDTMLDocument
to hold book reviews.

The document ("raw" property) contains the review, and I have created
a property sheet, "Properties", to contain variables such as:
-bookTitle
-bookAuthor
-bookPageLength
-reviewer

The BookReview class has a method, "index_html", that orchestrates
this information into a standardized presentation.

I would like to add the ability to add an image of the book cover to
the property sheet, similar to the way that someone can add an icon to
a ZClass in the basic view.

The closest thing I have seen is adding the ObjectManager class to the
base of "BookReview" and creating a method to upload a file into it. 
This however does not allow our writers/editors to accomplish this
task from within the Properties view of the instance of "BookReview"
they just created.

Any advice, direction, or better method would be appreciated.