I think Cursed Minotaur is an option you might want to add, others would include Binding Mummy to tap down blockers, Mummy Paramount which can grow pretty big, Tattered Mummy which works well with Diregraf Captain, Wayward Servant to gain life back and of course the good ol' Diregraf Ghoul.Also Time to Reflect is wonderful in Zombie Tribal Decks
While Vraska does need to react to a metagame to be truly strong, the card definitely has potential to see play in Standard, Pioneer and Commander
Brimaz, once the proud and brave king of the Leonin on Theros, is now a corrupted Phyrexian cat, built to proliferate the +1/+1 counters on the Incubator tokens
Whats really cool about Sheltering Ancient is that the ability doesnt target, so we can get counters onto creatures with shroud, hexproof, or protection from green (or any other quality Sheltering Ancient might have)