Love the idea! It actually got me in the mood to start drawing on furniture, not sure my roommate will be pleased :)
I truly believe creativity is optimal whenever one feels they are in a safe environment. In this case, I believe it's important that the contributors to that white room, be it kids, or even adults, feel they can express themselves without being bullied by their colleagues. In order to foster a safe environment, contributors should therefore be educated about the importance of giving one the freedom to express themselves creatively. The former comes from a personal experience which led me to lose confidence in my own creativity: getting bullied by schoolmates.