So i did some more work, and learned some more things: - i think in the above there are some errors - it seems that you have to parse the field into the blob_info object before you call form.accept. at least when i made some changes to my code today it was broken until i moved that. - i also created a single function that self-posts for the image work, i've included that below. I learned that when i wanted to customize the form with a sub-set of fields my function above was not quite generic enough. here is my custom form function: (lightly tested, so there might be some bugs)

@auth.requires_login()
def upload_art():
  """
  This is where an artist uploads a work of art.
  """
  form = SQLFORM(db.artwork,
                 fields=['title',
                         'type',
                         'completed_date',
                         'image'])

  if request.env.web2py_runtime_gae:
    from google.appengine.ext import blobstore
    import uuid
    #get the blob_info.  NOTE this MUST be done before any other operations on
    # the request vars.  otherwise something modifies them (perhaps the form
    # validators) in a way that makes this not work
    blob_info = None
    if request.vars.image != None:
        blob_info = blobstore.parse_blob_info(request.vars.image)

    upload_url = blobstore.create_upload_url(URL(r=request,f='upload_art',
                                                 args=request.args))

    form['_action']=upload_url
    if form.accepts(request.vars,session, formname="artworkform"):
        #@TODO: can this blob-key update be a post-validation function?
        #get the record we just inserted/modified
        row = db(db.artwork.id == form.vars.id).select().first()
        if request.vars.image__delete == 'on' or \
            (form.vars.image != None and (row and row.blob_key)):
            #remove from blobstore because of delete or update of image
            key = row.blob_key
            blobstore.delete(key)
            #remove reference in the artwork record
            row.update_record(blob_key=None, image=None)
        if form.vars.image != None:
            #add reference to image in this record
            row.update_record(image = \
                "artwork.image."+str(uuid.uuid4()).replace('-','')+".jpg",
                blob_key = blob_info.key())
        crud.archive(form)
        #Raise the HTTP exception so that the response content stays empty.
        #calling redirect puts content in the body which fails the blob upload
        raise HTTP(303,
                   Location= URL(r=request,f='index'))
    elif form.errors:
        #logging.info("form not accepted")
        logging.info(form.errors)
        session.flash=BEAUTIFY(form.errors)
        #there was an error, let's delete the newly uploaded image
        if request.vars.image != None:
            blobstore.delete(blob_info.key())
        #Raise the HTTP exception so that the response content stays empty.
        #calling redirect puts content in the body which fails the blob upload
        raise HTTP(303,
                   Location= URL(r=request,f='upload_art'))

  return dict(form=form)