Yes, Illidan has the Skull of Gul'dan - it's even a trinket that drops off of him in-game! Also, this is an absolutely beautiful drawing, and it represents Gul'dan better than even a Blizzard concept artist could.
Love to see what would be your take on like a full shot of Gul'Dan or maybe even a Durotan father of Thrall Chieftain of the Frostwolf Clan, Broxigar the Red, Origrim Doomhammer, or Saurfang. Major orc fan and player. Also admire a good wow orc rendition when I see one. Oh the possibilities! Keep up the amazing work.