Hi, sweet standard zombie deck! I like that you're really going for the tribal theme and actually have ways to fill your graveyard. One guys that comes to mind is
Advanced Stitchwing. He's not as powerful as
Geralf's Masterpiece, but he can get back on the field faster and for fewer cards. I can imagine T2
Wailing Ghoul or
Screeching Skaab with
Advanced Stitchwing going to GY, then T3 return Stitchwing to play discarding a
Prized Amalgam which gets to immediately return. Just seems to fit the curve nicely and something to think about.
With
Gisa and Geralf already in the deck, you have plenty of recursion, but i was wondering if you considered a couple copies of
Cemetery Recruitment? Early on, it can be a nice way to pull a
Relentless Dead from the Yard and lets you keep digging for win cons. Plus, even if
Gisa and Geralf are in play, you can still use it to get back a
dead Liliana, Heretical Healer.
Overall though, the deck looks pretty solid and I'm excited to hear how ti works for you! Good luck and Happy Hunting