@Riot I have a copyright question on splash arts

Say I really wanted a T-shirt with Renekton on it, particularly my favorite skin, Rune Wars. Let's say I know I can't just take the image and slap it on a shirt and call it a day, because splash arts just straight up on a shirt would probably look weird and be illegal. So what if I took the splash, made an outline of renekton alone, filled in his hands and feet, maybe tail that get cut off in the splash, and just fill in some lines, kind of reverse engineering the lineart of the splash. Could I put that onto a tshirt? Would I need written permission from Riot? The artist who designed the original splash or just Riot in general?

I own the skin already. I love Renekton, and I would only be ordering one shirt for my personal enjoyment alone. I'd tell people where it was from, and people that knew the game already would say oh boy renekton and then we'd talk about league.

If someone could point me in the right direction to getting permission to do this, or if I can even have permission to do this, I would greatly appreciate it.