Advances in eye tracking technology have enabled new interaction techniques and gaze-based applications. However, the techniques for visualizing gaze information have remained relatively unchanged. We developed Iris, a tool to support the design of contextually relevant gaze visualizations. Iris allows users to explore displaying different features of gaze behavior including the current fixation point, duration, and saccades. Stylistic elements such as color, opacity, and smoothness can also be adjusted to give users creative and detailed control over the design of their gaze visualization. We present the Iris system and perform a user study to examine how participants can make use of the tool to devise contextually relevant gaze visualizations for a variety of collaborative tasks. We show that changes in color and opacity as well as variation in gaze trails can be adjusted to create meaningful gaze visualizations that fit the context of use.