After the picture is exported, you can save it’s file path to a text file together with other fields from the document.
You can also simply save the XML output from exporting the whole document without going field-by-field. You will get a lot of unnecessary info, but it will not hurt. You can also specify a NotesDocumentCollection as export option and export all the documents to a single XML file. Later on you can parse the BASE64-encoded pictures to disk.