Early design space exploration (DSE) is a key ingredient in system-level design of MPSoC-based embedded systems. The state of the art in this field typically still explores systems under a single, fixed application workload. In reality, however, the applications are concurrently executing and contending for system resources in such systems. As a result, the intensity and nature of application demands can change dramatically over time. This paper therefore introduces the concept of workload scenarios in the DSE process, capturing dynamic behavior both within and between applications. More specifically, we present and evaluate a novel, scenario-based DSE approach based on a coevolutionary genetic algorithm.