A few cards for your consideration are Nissa's Pilgrimage, Basilisk Collar, Grappling Hook, Nessian Wilds Ravager, Pounce, Prey Upon, Savage Stomp, Woodland Bellower, Avatar of Might, Hunted Troll, Worldspine Wurm, Polukranos, World Eater, Garruk, Caller of Beasts, and Phyrexian Dreadnought.

Many of those cards were present in previous versions of the deck, though I later decided to take them out in favor of something I deemed better (for example, Hunted Troll and Prey Upon for Khalni Hydra and Ulvenwald Tracker are a couple that comes to mind). I also already thought about taking out Cultivate for Nissa's Pilgrimage since the latter would be strictly better, but despite it being a very common and cheap card I just haven't been able to find it yet.
That version of Garruk is very appealing though, as are the equipment options for Ghalta (I was also considering a Sword of Vengeance). The problem is that finding a spot for these trinkets is proving hard, I don't want to make this deck too much general-centric. Anyway thanks for the suggestions!

Magus of the Candelabra could be a good cut since it really only synergizes with Nykthos. Perhaps this card would be worth it if you also ran Growing Rites of Itlimoc . Though, Selvala, Heart of the Wilds seems like a better fit in general.

Verdeloth the Ancient and Dauntless Dourbark are kind of meh since you don't have enough Treefolk to good along with them. Avenger of Zendikar could be a better option than Verdeloth at least.

Timbermare is kind of a double edged sword since it also taps your creatures and 5 free damage isn't enough to warrant its cost, if this was a Yeva deck I could see it, but it is not great here.

Heroic Intervention seems a bit too reactive rather than proactive, this could be something like Swiftfoot Boots. The Hexproof will protect from targeted removal just as well and even if they do kill your threat, the 1 mana haste will just let you swing back in the following turn.

I also don't see any synergy with Walking Ballista so it could also get cut if need be. Same for Aetherflux Reservoir, you really need to commit to a life-gain strategy to make that card worth it. Sure it gains you life on its own, but how many spells do you normally play in a turn? If I wagered a guess, I would say 2-4, but even at the high end that isn't much in this format.

Lastly a few other cards you could make use of are Traverse the Outlands and Pathbreaker Ibex.

Growing Rites of Itlimoc  ^Flip and Avenger of Zendikar are already in the deck. :)
The Magus is also good with the mana doublers Caged Sun and Vorinclex, Voice of Hunger, though Selvala would be awesome nontheless.

You are absolutely right regarding the treefolk sub-theme, but Verdeloth the Ancient can be good on its own, putting a lot of power on the board, being a good finisher for the combo, or even just baiting a mass removal. Dauntless Dourbark, on the other hand, can be a 4 mana huge creature depending on how many forests you have in play, but I admit it's mostly here because the deck used to run more treefolks (like Kalonian Twingrove and Seedguide Ash), so I'll probably end up cutting it, maybe for a Pathbreaker Ibex, a Craterhoof Behemoth or something of the like.

Heroic Intervention is indeed very reactive, but my meta is full of mass removal and the card has proven its worth many times, so I don't think I'm ready to bid it farewell yet :P

Walking Ballista and Aetherflux Reservoir are mostly in the deck as finishers for the main combo, and while the first can eventually do something on its own, in case of not comboing off, I agree that the Reservoir would be completely pointless. This part of the deck is still under testing, but I may very well decide to cut it in case other finishers prove themselves consistent enough.

Thanks for the suggestions! (I feel like I should make the deck's description more visible, lul)