As far as I am aware, the only limitation is on the amount of new animation types, as in different attacks and stuff. I don't think there is a limit to adding to critters of a non-player type. Then again I don't really know what I am talking about. Contact X'll he/she is the person to talk to about this.
edit
By the way, some of your stuff looks nice, but the shiv on a pole in your first post will cause people to dismiss you. I would make that disappear then make some more sexy stuff.