I love the balance of cards submitted so far.
The official Zombies are well-designed to offer balance, choice, growth, etc. One of them has you trash an Action card (setting up future possibilities for the next Necromancer) for great gain. Another has a possibility of trashing an Action card, still at a moderate gain for the person who played it. And the third is a catch-all remainder/fallback, being a cantrip.
Many of the submissions so far continue the same possibility of putting in more Action (and Treasure, for the Throne of the Dead) cards for future use. (A note - Throne of the Dead itself doesn't set up for its future use, and it would have to rely on the luck/usage of Zombie Mason, if the kingdom was absent of other Trashers, so this is a definite drawback). But I like the idea of encouraging growth of usage, not just putting a unique (possibly slightly powerful but not overpowering) card in the trash and calling it a Zombie. On this point, my submission is actually very un-thematic or unbalanced, so I'll probably change it.
I am trying to figure out another card/thing that could use the Zombies, meaning the Necromancer wouldn't be the only thing putting them in play/trash. It's a lot harder to work with this idea. Faust's Event attempts to do this. It looks like a really cool idea (effectively giving you an extra turn with only cards currently in the trash), and that adds extra variety/complexity to the submissions. But the Event is very complex in the wording. I'm not sure if it's intentional or not, but any card you gain with that extra turn would not remain yours... it would go back into the trash after the second swap. Alternatively, the upside to that event is that you could use a Zombie Apprentice and "trash" a Zombie Spy, Zombie Mason, or other card that was in the trash, which means it goes into your hand after the second swap... I'm guessing this is the main intention of the way the Event is worded?