Emotive virtual agents are seen to be a valuable tool in various research domains, including human studies, training, entertainment, and medicine. However, systems that primarily focus on social-emotional agents are largely domain-focused, or require ample customization to make them usable. The importance of agents that display social emotions and behaviors is underscored by the use of social strategies such as favors and ledgers in negotiation contexts, as well as in other domains. A set of core design principles for the next generation of virtual agents is proposed that will result in more robust and varied virtual agents. This early-stage extended serves to illustrate the core principles and continuing research efforts regarding social virtual agents. Categories and Subject Descriptors I.2.11 [Artificial Intelligence]: Human-agent Interaction – virtual humans