The Red Duke is a Brettonian, currently inhabiting Mousillon. They're have been other rulers of Moussilon who dabbled in necromancy or vampirism but he's probably the most famous.
For a Mousillion themed army i would go with Brettonian Knights for Black Knights, Men at Arms for skellies and zombies and ghouls can stay as they are. Given the Brettonian penchant for force of arms i'd stick with mainly vampire characters, combat focused, with necromancers for support.
Some alternate Blood Dragon models (who originally come from an Empire Knightly Order actually) i would recommend GameZone miniatures Vampire Knights as alternate models if you're interested; they're fantastic.