Surprise Party Lissandra
I've had this idea since she was released, but judging by her current popularity in pro play I think this concept might find a more accepting audience now. First off, my buddy mains fiddle and always uses the surprise party skin. Nothing brings me more delight than watching enemies squirm as that adorable ulti flies in. Lissandra shares a similar aspect in that her ulti instantly changes the course of a teamfight so a surprise party skin is a good fit with her. Also, she has a kind of "I'm super mean and serious" vibe to her that may warrant a more light hearted feel.
So starting off, she rides a unicycle. That may be extremely hard to make function in the game, but if it can be done it would make sense. She already has a fluid movement to her and she's elevated very high. Put her on a unicycle. As for attire I'm thinking she's dressed as a clown with one of those cheesy clown wigs that has the poorly made bald cap with hair that shoots out the side. The hair would serve to keep up with the 2 spikes jetting out the side of her head.
Abilities.
Q: She throws a pie. I mean come on. How great is that? She throws a pie and the cream acts as the backsplash to replace her ice chunks. Can u just imagine being in lane and besmirching your opponent by constantly throwing pies at them?
W: This may seem odd but I think it should stick with the pie aesthetic. Chunks of pie (possibly cake) fly around her sticking enemies to the ground.
E: This one I can't really figure out. I'm thinking a group of pinwheels skating across the ground.
R: She slams a giant cake down. Whether it be on herself or an enemy a giant cake would be perfect. A quintessential tiered cake that encases whoever it lands on.
I'm not really artistically gifted so I don't have any concept art, but it would be cool if someone took a crack at it. Similar to the way that gentlemen Cho'gath or Corporate Mundo do, I think this skin would make games and teamfights so entertaining no matter if you're wearing the skin, it's on your team or if it's on the enemy team. If you guys like it let me know. If I'm an idiot and it's the worst idea ever..... let me know also.