For one, just to keep the trend of Air going, I think it should be an airborne creature. Also Thalas has made a picture that looks pretty good with its wings, so how it looks shouldn't be an issue. The effect still escapes me as to what it should be. It will definitely involve adding poison damage to the opponent, but the unique effect should involve forcing a condition upon the opponent based on the poison counter; the capability of the venom, triggered by certain circumstances (like Dune Scorpion), or constant effect like as is; or a passive skill. A blowing scorpion might actually be a good idea though.
Just the passive of airborne seems a little soft, compared to auto-burrow of the Earth one; since it only refers to other Air cards, and I think the Warden.