Nothing that really stands out as a Must Have card, but there are a few you could consider.

Amonkhet has Anointed Procession, Anointer Priest, Regal Caracal, Dusk / Dawn, Bontu the Glorified, Trespasser's Curse, Start / Finish, Bontu's Monument, and Oketra's Monument.

Aether Revolt has Sram's Expertise, and Hidden Stockpile.

If you go back to Kaladesh though, there are some strong cards worth considering. Authority of the Consuls, Kambal, Consul of Allocation, Aetherflux Reservoir, Animation Module, and Key to the City.

Commander 2016 has Tymna the Weaver.

I love Authority of the Consuls. Thanks for the many ideas, I will think about them.

I like how Animation Module can combo with Karlov and a creature like Soul Warden. Karlov gets a counter, the Module triggers and you pay 1 for a token, which triggers the Warden to net you a life and then Karlov gets two more counters. Rinse and repeat for as long as you have mana to pump into the Module. It's not quite as good as the Thopter Foundry + Sword of the Meek combo, but it does give you the ability to basically get 3 tokens and kill a creature with Karlov for 3 mana.

Sorry, I meant "Get 3 tokens and kill a creature with Karlov for 5 mana."

Yes, yet another nice card to consider ...

adding an Ashnod's Altar or Phyrexian Altar would make karlov go infinite with that module combo (need some sort of mana filter to exile stuff though)

Didn't even consider that infinite combo. However, I don't see much other good use of the Altars in this deck when the combo doesn't stand. Not sure therefore whether I should take the risk and play a card that only does well in the combo and which is not very purposeful otherwise.

You should consider Alliance of Arms for this deck then. It is a cheap token generator that costs 1 Mana and you only need to pump when it resolves, so it can't be countered then. With Cliffhaven Vampire or any of the other Lifegain triggers + Soul Sisters or Authority of the Consuls it can win the game instantly. 5 Players, 5 extra mana, 25 tokens, 25 life trigger + 25 damage to all players. Even if Cliffhaven is missing it gives Karlov +50/+50 then.

Very cool card. Thank you! I will consider it and most likely play it.

Alliance of Arms also works well with Sanguine Bond, Defiant Bloodlord and Suture Priest, and it helps with cards such as Aetherflux Reservoir or Test of Endurance - so rather versatile and therefore a winner :-)

Very nice! I will add some cards I've seen here on my deck. Upvoted!