Form what I can make out it is either a plaid or a kilt.
That thing around his waist is a sporran, so my bet is on a kilt. (Kilt and sporran are traditionally worn together.)
Oh, I personally think that a plaid would fit better to a fantasy theme, though. The kilt was introduced to Scotland around the 19th century and is considered a formal dress.
The plaid however was forbidden to Scotsmen after their defeat in the Jacobite uprising. As the bagpipes, the plaid was viewed as a weapon of war and wearing one (or playing the pipes) would get you hanged.
Greetz,
Tex