Over an eighteen-month period, Tamaddon worked closely with founder Jacqueline Sullivan as a strategic consultant to support the establishment of Jacqueline Sullivan Gallery, shaping its identity and positioning within the New York art and design landscape. She advised on public programming, client development, staffing, and institutional strategy, contributing to the cultivation of a distinct curatorial and market voice aligned with the gallery's concept driven approach to contemporary and historical design. Tamaddon also collaborated on the development of off site and satellite initiatives, including the gallery's participation in Frieze London's The North American Pavilion, presented alongside Tiwa Select, Bruises, Marta, Studio Ima, Emma Scully Gallery, NOON Projects, and Of the Cloth.