I didn't know /imagine could be followed by a prompt, but similarly I asked the avatar about it's appearance and stated it had none. Should probably give it the context of what it's appearance is like, same thing happened for questions like where are you? What are you holding? Who's that behind you? etc etc
This is so obvious now that you say it (* facepalm *). We definitely need to give the LLM context on the appearance (both from the initial image as well as any /imagine updates during the call). Thanks for pointing it out!