William is a pretty cool looking character--is he finished? If so, the paintwork is pretty basic; again, I'd suggest some washes or dry brushing to kick things up a notch. The white areas would probably look neat with some kind of pattern on them too (dragons, or whatever). The Yakuza are well known for their elaborate tattoos as well (although they generally cover them in public), that might be another idea for spicing up the appearance on the arms.
Here's another quick one I recently finished, a 'Mammon' from Final Fantasy IV.
More photos/information.