Among the advanced specialties which one would better picture a wolfguard? Have anyone made a custom one?

I'd say First Company Veteran is pretty close in intent.

I would use the Honour Guard with some modifications to the requirements.

What modification do you use?

Change the talent requirements to Wisdom of the Ancients. Change the wargear to Terminator armor plus weapons. If you don't want to add Terminator armor you can always add one of the other Wolfguard specific items like a Frostblade or a master crafted power weapon. Perhaps a Thunderwolf or Fenrisian Wolf companions for free.