Customer inputs in the early stages of design can potentially lead to completely new outlooks in concept generation. We propose crowd-based co-creation as a means to this end. Our main idea is to think of the customer as a source of initial design concepts rather than a means for obtaining preferences towards designer-generated concepts. For analyzing a large collection of customer-created prototypes, we develop a framework that focuses on generating hypotheses related to customer perception of design attributes. We demonstrate our approach through a web interface to gather design requirements for a computer mouse, a bicycle seat, a pen holder, and a cola bottle. This interface was used in a crowdsourcing study with 253 users who represented potential end users for these products. Results from this study show that web-based co-creation allows designers to capture a variety of form and function-related design requirements from user-created virtual prototypes. We also found that such studies can be instrumental in identifying innovative product concepts, and gaining insights about how user perception correlates with product form. Therefore, we make the case that customer creation through distributed co-creation platforms can reinforce concept exploration in future early design processes.