Watching a video showing all customizations so far (I'll direct to it below) I could notice some very interesting things, possible spoilers maybe, but mostly nice references to the whole MK Universe that I'm not sure if we shall expect more:

In the Sub-Zero menu the Tengu are mentioned. Could MK11 bring back this Lin Kuei minor rivals? It's possible since they habitate Lin Kuei Temple's region;

Raiden has two version's of Shinnok's Amulet. One of them the middle jewel glows in the same color of his lightning (I can see that because his original MK9 Amulet turns red if he's Dark Raiden). With a version like this, could Raiden unlock a different power of the Amulet? Maybe bound it to him in a possible redemption? (Could be only a customization feature, but it's curious to have two versions);

Raiden has two outfits that have names. Meldius and Cairies. Possible name of Elder Gods? Other Gods? Heroes of the old? MKX had Mordulus, but there was never mention of that, could be another dead end either. Funny the latin like names;

Reiko's ritual blade is a type of blade for Skarlet. Guess this could be saved from MKX comics at the least;

Blended *Meat* Juice for Skarlet. Eeks;

Geras has a piece for his back called "Last Days of the X Era". Could this be a nod of the once again retelling of MKX story?;

Geras also has one called Crystalized Jinsei Essence. His blood is blue and he glows blue. I was wondering if Geras isn't powered by the Jinsei or a similar power. As Kronika also glows that blue, reminds of my loose theory - based that the One Being is also that color - if the Jinsei isn't actually the heart of the One Being and Kronika and Geras (the second most likely a construct) are related to him directly;

Pax Edenia is a reference to Pax Romana, time where Augustus was the Emperor and the Roman early Empire saw a very prosperous moment after half millenia of turbulence in the Republic;

One that I have mentioned before, a chest emblem named Totem of Immortal Onaga. I still don't know if I should get my hopes. Afterall, he's immortal...;

- Another one VERY interesting. "Faithful Servant No More". Could Geras betray Kronika? Well, Raiden did wanted to induce him to cut the ties with her in one of the intros.

Video:

Video: Mortal Kombat 11: ALL Gear Showcase, Skins & Special Moves! - Mortal Kombat 11 Customization