I show mine. I'm not always happy about it, but it is presented in an attempt to be honest, open, and trusting towards the other board members. I feel really androgynous - a fact that I'm having a conflict with presently. Androgyny is fun, and I can make an attractive young woman. But I'm frightened by the fact that I can be an attractive young guy, too.
Perhaps it is the same with the others. Wearing an avatar usually requires some self-esteem, and to someone that hates their appearance from the core of their soul, putting a picture of oneself to their profile would be difficult to do. It's like how I was with my voice... when I had to use my male voice, I despised talking, and cringed every time I was made to. I have since put an end to this, but I will never forget how that felt.
... I don't believe that I needed to say any of that, but it feels good to say.