Page 49 of the Novus core rules contains several Combat Moves for using a shield offensively.
Require "Shield Training". This grants a +1 to DEF of the shield, then the Combat Moves say Damage is DEF+St. Now, considering that you said Martial Artist, then let him do a Weapon Kata using the shield. This adds another +3 to the Base Damage (i.e. a Target Shield learned in this manner would give+3 to DEF, and have a Base Damage 6+St, a normal shield would be +4 to DEF and 7+St for Damage, and a Full Shield would be +5 to DEF and 8+St Base Damage (and -1 point of Base Damage when thrown).
And this is BEFORE you take into account material/construction/design of the shield.
As for the range increment - normal would be the same as for any thrown weapons (i.e. th = thrown; range increment for thrown weapons is the Strength Stat Value of the character in feet.) With shields that are aerodynamic being 2x th, or depending upon the material that they are made of, up to 3x th or even 3x th. (I would make it depend upon the final weight of the shield and how aerodynamic the shield is.
