No idea if he's CG or practical. I'm hoping practical. However, since he is mechanical, they may be able to have him look quite good in CG. Mechanical tends to look much better in the computer than anything organic, due to simple rules of physics. It's easier to predict how light will reflect off of a smooth metal surface than how it'll bounce off of skin, pores, hair, scales, and all of these things that are so random in their appearance. That's why (to me) the battle droids look pretty convincing, while the Gungans look utterly unbelievable. Give me rubber puppets any day, at least they'll be tactile.