Nice work, & very nicely presented! The Vampire Coast was a really cool corner of the Warhammer world, so it's always good to see something being done with it. Some things to correct or clarify in your list:
-The 'Habituation' special rule doesn't make total sense here, since it talks about von Carsteins. Presumably the rule applies to the Necromancer, so it's worth including, but needs rewriting for this warband.
- Most entries lack a "Weapons/Armour" category. Does this mean Zombies can take weapons? This is worth clearing up, since usually Zombies can't take weapons; if you mean they can in this list, you should point it out.
- For the swivel gun, I'd include the option of firing grapeshot using the Mordheim blunderbuss rules, in case anyone doesn't have a flamer template. Not everyone does, & GW go hot & cold on making them, so it's maybe worth putting in as a note.
- "Weapons Locker" shouldn't have an apostrophe in it. Sorry, it's a small thing, but also fairly easy to correct, especially when the rest is so well presented!
I'm also concerned by the price of First Mate, & the lack of experience for Wightmates. The First Mate costs about the same as a human champion, has an equivalent stat-line, & gets all the vampire special rules, which makes them seem a cheap option to me. This might be off-set by the quality of the henchmen, but it's definitely something I'd keep an eye on.
As for the Wightmates, I worry that not letting them gain any experience will make them rather boring hero slots, & limit the fun of the warband in play. Basically, they become henchmen who lend an exploration slot, rather than characters that can develop. & in the Warhammer fluff (or lore, if you prefer), wights could redevelop the skills they'd had as living warriors (mighty human warriors could return as powerful wights, like Krell), so letting the Wightmates gain experience makes in-universe sense. That's included in the Tomb Guardian list too.
Overall though, this is a pretty damn good warband list!