For example, the following video started as a fan creation, and then became a collaboration between the composer and visual effects artist. And the composer attributes his relative success largely to the success of the video.
Or, you're probably familiar with the music/design/performance art project that is the Gorillaz. Here, an artist and some musicians have collaborated to simultaneously create these characters that navigate this cool transmedia narrative (oftentimes, in a cool, camouflage dune buggy). Here, neither image nor music has primacy--they're simultaneously produced and thoroughly interdependent.
One is more abstract; the other is more narrative- and character-driven. One attempts to visually represent tone, pitch, rhythm, instrumentation, etc.; the other is interested in using the combination of image and music to build a world. I invite you to do what you think most authentically expresses your reading of the music.
I know that that's kind of vague, so I'll attempt to be a little more concrete (as concrete as abstract expressionism can be, I suppose). Jackson Pollock was rumored to listen to jazz as he painted. So, if little Jack was taking CRV, he might choose some piece by Miles Davis and then be inspired to paint the following image.
So, he likes this pairing of image and sound and so he continues to listen to the piece, noting different aesthetic elements or emotions or whatever, and then produces a series of images to accompany the piece of music.
Then, maybe he decides to experiment with the size, shape and composition of these images. In this case, perhaps, the layout corresponds with the chronology of moods he experienced listening to the piece a given time.
Ultimately though, Jackson Pollock never had (or at least he never bothered) to justify his artistic approach to anyone. You will. Whatever the medium, form, content, etc. of your mosaic, you'll need to be able to explain their significance.
So, refer to the description of the assignment in the syllabus, our discussions in class, the feedback you got during the workshop. Then get to work. Remember that your completed assignment will include a 300-500 word 'artist's statement' that contextualizes your mosaic within the week's topic--in this case, this delicate process of creative inspiration and execution.