If you’re looking for practical information and guidelines for implementing multimodal composition assignments, I highly recommend that you check out Cynthia Selfe’s book,
Multimodal Composition: Resources for Teachers.
Here is the product description from Amazon:
Multimodal Composition is designed to help teachers of English composition expand the modalities on which they and their students draw, to go beyond the limits of texts that rely primarily on words, and to enjoy exploring the affordances-the special capacities – of video, image and sound. This book offers faculty practical help on creating multimodal assignments and working within digital composing environments.