Pentakill Idea
(I'm gonna preface this by recognizing the amount of work this would require, however I still think it's a cool concept)
Since their are so many champs, and in sticking with the original PentaKill idea of it being a band, you could make Pentakill skins for everyone, but it would be like a dark, goth-y Orchestra. So Teemo would play the flute, etc etc, Vayne could have a Violin, get creative as you so choose. However, the catch would be, that the only way to get a Pentakill skin would be to actually get a Pentakill in the game. It would add a uniqueness to the skin.
So just a random idea, probs gonna get shot down.