I remember trying so hard to build Sultai Midrange/Control with Grim Flayer as a Tarmogoyf replacement back in the day. The thing is, it's so hard to grab Delirium quickly in a deck that has so few card types, and playing Tasigur, the Golden Fang alongside the Flayer makes for some really awkward times. Nevertheless, I have a few suggestions that may or may not sit well with you depending on your style of play and funds.

Mishra's Bauble is invaluable for a deck like this. Alongside a fetch, it essentially says "Scry 1, draw 1." It also can give you information as to what is on your opponent's library, which is understandably less valuable since you have Thoughtseize and Inquisition of Kozilek. It's also an artifact that puts itself into the graveyard for free and replaces itself, which is crazy good for turning on Delirium. Downside is, obviously, the hefty pricetag.

Courser of Kruphix gains you life, gives you lands, is a great blocker, and works very well with fetchlands. He's also an enchantment, which works for Delirium. Downside is that investing three mana into a creature on turn 3 is probably not what you want to be doing, especially if that creature becomes a target for the cheap removal spells that permeate Modern.

Garruk Relentless  ^Flip is a green, 4 mana Lightning Bolt with upside if he sticks. While he's certainly not the best card in Modern I think he works well in this deck, as he usually puts himself in the graveyard along with an opposing creature. Downside is investing the mana into a Planeswalker that possibly just does nothing is quite bad.

I think Mishra's Bauble would be a great include and I did think of it but I just can't justify buying for 41$ a piece right now.

I don't know exactly about Courser of Kruphix but it could be tested.

Garruk Relentless  ^Flip Seems very interesting and I might try him as a one of and see how it goes.

Thanks for the comment @PhyrexianScience . Do you play Sultai at all anymore/ would you think about testing this list?

I built a Sultai mid-range deck a little while ago, and I don't think Liliana is where you want to be. Liliana works best when you are hellbent, and snapcaster plus counterspells does not make that a strong proposition. I run a Dark Confidant build, so it's not going to be exact same as yours, but tarmogoyf is still a huge reason to run green in modern. I also like damnation more as a sideboard card in these types of decks because you're trying to pick off your opponents creatures with one for ones, and Damnation it's just a debit card if you're ahead on board, which you will be a decent amount of the time.

I agree with the Liliana of the Veil pick But idk who is a good replacement. Maybe Jace, Vryn's Prodigy  ^Flip?. Lili seems off with this type of style. As for Maelstrom Pulse and Damnation those are usually situational cards and usually have 1. Damnation usually is in sideboard but I feel it fits in main here. In replace of these I would grab a 4th Fatal Push and a 4th Inquisition of Kozilek. When it comes to your lands I think running 4x Blooming Marsh. These benefit you because they are immediately playable if you have them in starting hand. I personally love cards like Thragtusk and Kalitas, Traitor of Ghet for life gain but with Kalitas you get tokens and pump him up, Especially since you have kills spells! As for Cryptic Command I feel it costs too much but I'm not an expert on blue lol. hope this may be a bit helpful as well! I run a Jund modern and am still slightly new to modern but I love it so far! I also enjoy this style because it's different.

Now that I'm looking at the deck again you have Darkslick Shores for another fast land. So I would think either 2 of both the fast lands, or 4 of one.