The COVID-19 pandemic has led to the proliferation of non-face-to-face video-mediated communication such as through ZOOM or Google Meet. However, video-mediated communication has several limitations related to exchanging vocal reactions and non-verbal expressions. Consequently, although current video conferencing platforms provide visual support through icons, it remains challenging for users to express various intentions because of the limited number of icons, their uniform size, and their fixed location. In particular, these limitations challenge designers who require collaborative design processes such as brainstorming. To investigate user needs related to icons that better support video-mediated communication, we conducted a participatory design methodology. Based on the analyses of participants' brainstorming experiences with various icons through participatory paper prototyping, we found that icons that accurately reflect diverse user needs facilitated turn-taking during the design process, and allowed participants to exchange more opinions and emotions. Thus, they created a positive atmosphere in the online meeting environment.