Always love to see decks built around my favourite card! This looks like a solid build, and the focus on one-drops should help it build up quite quickly.

Some other suggestions I think you might like to consider:

Vengeful Dead is nasty with the Stairwell, since it triggers on each player's turn, and he counts each player's dying zombies. You can very easily wipe out multiple foes without even attacking if you pair these two together.

Twisted Abomination is a little slow, but he's a two mana way to grab another land while simultaneously putting another body in your graveyard. And if you draw him in the late game, a 5/3 regenerator isn't too shabby!

Noxious Ghoul is a rude one, since he also counts everyone's zombies and will quickly wipe the board of anything that isn't undead. And of course, the more creatures die... the more zombies are showing up!

Gravespawn Sovereign: of course, you don't want your opponent to be getting too many zombies... since your own tokens can't attack on other peoples' turns, you can just tap five of them (after combat) to reanimate one of your foe's dead critters for free. Talk about adding insult to injury.

Sadistic Hypnotist meanwhile, acknowledges that all of your zombie tokens are dying at the end of each turn regardless. You can feed them to Carrion Feeder, of course, or you can also cash them in to empty out your opponent's hand in short order. Not a bad option to have.

Old-school poison is always a real charmer... it took a lot more work to get it to function back then, ha ha.

If you're interested in making a mess with the old Thicket Basilisk and Lure combo, you might prefer Sylvan Basilisk in his place. The Sylvan wipes creatures as soon as it's blocked, not at the end of combat, ensuring he's never killed by blockers. For what it's worth, he can also bring down walls! Another good alternative is Elven Warhounds, who are one mana less and don't kill the blockers... but possibly do something even work! They stuff your opponent's creatures on top of his deck, forcing him to just draw the same cards again. This can buy you tons of time to finish a foe off, as he either has to keep replaying his creatures (accomplishing nothing) or just sit for a few turns until he draws through them all and then hopefully gets a noncreature way to deal with things. It's pretty delightful!

Demonic Attorney.

Give me your cards, nerd.

I dub thee "Snowtus."

This is a cool idea, but I feel like Throne of the God-Pharaoh is just the better win condition. It's less mana to play, takes no mana to use and doesn't require coloured mana. Halo Fountain needs five white mana for you to win, which is kind of a big ask in a two-colour deck, and needs at least fifteen tapped creatures to win. The Throne can kill your foes off in a couple turns even if you only have ten tapped creatures. The Fountain is fun, but I can't shake the feeling that you'd be better off cutting some for more Thrones!