The following champions could do with a splash art update
First off, I'm not criticizing the splash team. I think they're wonderful. Think of this more as a checklist so to speak.
I'm using what I call the Zyra Quality Check. Starting from Zyra onwards, you can see a noticeable spike in splash art quality. So...
Old Splash arts - Season 2:

Old Splash arts - Season 1:

Chinese Splash Arts:
These champs use their chinese splash arts and need new ones.
You'll notice I didn't include Nautilus or Draven in there. Honestly, they're perfect the way they are.
That's all as far as I'm aware of. Really shows how much the art team cares, 119/133 is really great.