White Cards
Ascend from Avernus - Since the curve on this deck is fairly low, this ends up being a 5 (maybe 6) mana mass reanimation spell. While Rally the Ancestors is a bit better in how well it returns things, it would be exceptionally difficult to get any real use out of it since I can't attack with most things. This spell, on the other hand, allows me to rebuild and then hopefully swing out.
Battle Angels of Tyr - Again, another draw engine but one that also offers life gain and ramp. I should be able to swing at one person at least without the Angels dying (and hopefully getting through with the token copies to the person I need to). It is, again, not a Legendary permanent, but the effect seems like it could be really useful here. There is always the possibility I just can't damage the person I need to for the effect I want. But, even then, it is still three 4/4 fliers going at people.
Cut a Deal - This is a bit interesting in comparison to Secret Rendezvous. It spreads the aditional cards around, which is nice as it doesn't put someone that far ahead of the others (other than us) but it also doesn't scale well since we can sometimes only draw a single card off this. I do like the effect and where things are moving, but I am not sure this is exactly where I want to be for card draw. I might pick one up just in case anyway, but it does look a little worse than Secret Rendezvous (which isn't exactly a great card to begin with). So I will probably pass for now.
Far Traveler - This is Legendary so it triggers Yoshimaru and it also blinks my tapped creatures to hopefully trigger Yoshimaru again. 3 mana is kind of high and it is sort of a slow effect but it could be worth it. I don't think I have a good place for it right now (especially with some other adds I want to try) but it is something I might keep my eye on.
Lae'zel, Vlaakith's Champion - Another Legendary permanent and it works well with Yoshimaru's counters. Again, 3 mana is sort of a lot here but it could do some work to really get Yoshimaru big. I will have to see whether I really want to pursue this though. At least with this, it is a creature so it is a bit better than a Background.
Lulu, Loyal Hollyphant - This would work wonders with Norin The Wary but 4 mana is a little higher than I would like. And without Norin, it is a bit tougher to really ensure it triggers so I think I will pass on this for now.
Noble Heritage - This seems like a pretty good way to increase the number of counters on Yoshimaru and I don't think I care all that much about my opponents getting counters on their creatures since, hopefully, Yoshimaru at least remains larger than their creatures. The way it plays out might not work that great though so I will think on this a bit more.
Your Temple Is Under Attack - This could be a decent card draw spell (and protection spell if needed). Since it is an Instant, it is a bit easier to get more immediate use out of it than the opponent who is also drawing cards so I think it might be worth trying out.
Red Cards
Tavern Brawler - This helps beef up Yoshimaru and acts as a sort of "draw" engine which could work out pretty nicely. Effectively, it is the half of Urabrask that only affects me but also beefs up either (or both) Commanders. Which, speaking of, since I have two commanders this can "draw" me two cards per turn which is nice as well.
Wild Magic Surge - Another red removal spell is good to have though it isn't quite as good as Chaos Warp. I am not entirely sure where this lies but it seems like a reasonable option. The main issue is that it gets the controller back the same permanent type so there is no way to "whiff" (unless they have no others of that type left) so it is less effective. It also destroys instead of shuffles or exiles which means indestructible stuff is pretty hard to deal with. I might pick a few up but there are probably enough cons with this card that for any deck that isn't mono-red, I think there are better options.
Wyll, Blade of Frontiers - Cheap Legendaries are always worth a second look but this one is pretty much worthless. Even Isamaru at least has 2 power and only costs 1 mana. This is a 2 mana 1 power "nothing" and it is pretty hard to justify it in the deck.