Multiple insert does support multipart/form-data... it works just like any other form. The thing that doesn't support repeated fields is the file upload server behavior itself. It could be done by storing the file fields in a BLOB in the database, but that is notoriously inefficient. The other solution is to hand code a WHILE loop around the file upload so that it would work with repeats. This is something we could help with in a 1 hour premier support ticket.