Bad splash art, great in game skins?
What's your take on the reverse of the question? Which skin do you think has a bad splash art but a great in-game model? I'm gonna say Infernal Diana for this one.
Many splash arts and even classic champion splashes have something going on behind them which is intriguing enough for you to want to learn more about it. We only see two people stumble, not even in a really eye-catching way and her running from it. Foxfire Ahri does this too, with the lackluster background; but Foxfire Ahri isn't a 1350RP skin.
https://2.bp.blogspot.com/-20JEbfMqm_0/VwQZHz2oryI/AAAAAAAANDI/uTgXImIP13EQF9BWo15f_lWLR7lrCSgMw/s1600/dianaturn.jpg In game, she looks as you would expect; no biggie. But... Infernal Diana makes up for this loading screen card disaster with her beautifully constructed ability effects that look like it would've been abilities for Brand or Annie if they were visually updated. https://2.bp.blogspot.com/-TLL6KG483n0/VwQG4OG-9xI/AAAAAAAAM-c/Jhz6okFRpg0rYqcPzC-ZP6m-hGZFAbt3A/s1600/lMaI9FQ.png
The sounds of the scorching and burns is also extremely satisfying.
Much more thrilling in-game than the splash art looks, trust me.
Oh, and don't even start me on the builds I'd make because of this... 
