Assessment should look at how the modes react to one another, how effectively they work together. Never a fan of rubrics, shouldn't all grading of verbal, written, or visual information be based upon the effectiveness of relaying the message. If it makes sense, then it has succeeded. If nobody can figure out what the message is, it has failed. Also, why do we worry so much over assessment anyway? I have constantly thought that the handing out of grades has more to do with punishing those who do not meet our (or class) expectations than it has to do with helping students improve. Once the grade hits the page, teachers become judges and not coaches.
images have more than one signified - linguistic messages fix these signifieds
space is political - visuals are political