[Vox]

Currently, the only avatar site that has more than one pose is Gaia. All the other ones are standing only. Ernya had one, but gave it up almost as soon as the site started. :(

A sitting pose would add more interest to avatar dressup, add more moods available to the members, and increase interest towards the site, as it would be extremely rare.
The best time to add a new pose is at the beginning of the site, when most items have not yet been fully created and implemented. I think a sitting pose would be awesome.