While mobile phones have become ubiquitous instruments of communication and social interaction, they still require explicit interaction, placing high demands on attention. Engaging the periphery of users' attention offers opportunities for awareness and interaction while reducing demands on attention and risks of disruption. We explore the mobile peripheral design space with Emotipix, an application for camera phones that turns the background of the phone's display into a place for visual conversations. We conducted an exploratory 2-week user study with 6 pairs and one 4-person group, and found that Emotipix facilitated ongoing social practices. Our study shows that there is an unexploited opportunity to use mobile phones for peripheral awareness. We provide recommendations for managing users' expectations, desires for control, and privacy in mobile peripheral display design.