Over the past few decades, there has been a marked shift away from conceptualizing literacy as a functional skill set toward its recognition, particularly for children and youth, as a social achievement that is buttressed, in part, by access to digital tools and new media. Yet, beyond the mere consumption of multimedia and the mundane assemblage of words, images, and other resources, we ask, "What does a successful multimedia literacy performance look like and how might "designful" multimedia thinking and composition be taught, learned, and assessed?" In addressing these issues, we present a fine-grained description and analysis of the work of a 13-year-old Singaporean named "Jeremy," who produced a personal digital story of considerable theoretical and practical interest to us as researchers and new literacy scholars. Building on prior research in the field of multiliteracies, we argue that educators (and students) must cultivate their own senses of "semiotic awareness" before meaningful assessment of children's multimodal design work can be conceived or implemented. We also sketch a preliminary approach to assessing multimodal literacies and explicate a range of interconnected representational possibilities that we expect will prompt a timely and urgent reconsideration of multimodal meaning design in school settings.