Ok, I understand your expanation.
Is there way to display the currently stored image file name on the update page. The note below from the "Adding DFP to DataAssist Insert & Update Pages" suggested to me that it would be displayed.
Change <input type=”text”> to <input type=”hidden”>.
Note: This is done to allow us to display the value for the form field that is currently entered into the database.
I would find it useful to see the stored image name before deciding if a new image was required.