I'd have thought that the P1 would be as good a choice as any, because his face is never shown its open to artistic impression. Personally I think it would be nice to do a Celtic design on the face/head or something to distinguish him from P1. Look at Pastry's post she's got a really cool tribal design on her Wolf.
As far as the neck ring goes I've not seen a celtic but could have just missed it, I'm sure an expert will chime in and help you out