There is no such campaign as you are looking for. Anyway as I know campaigns doesn't allow to a person would be in two signature campaigns at the same time, this rule was in every campaign where I was. So in the case if such avatar campaign will ever appear you will have to chose something one or you will be banned by forum's moderator.
What are you talking about? There are a couple of avatar only campaign in the altcoin section of this forum. Also, most campaigns are fine with you having an avatar campaign as that doesn't change your signature.