Not really much to say, just throwing ideas out there.
Bubblegum 
(Do you even need to ask?)
Cheshire Cat 
(I mean really... he already has the smile and looks cat-like.)
Doctor 
(All the other ninjas have a medical skin)
Thunder Bird 
(They already have a Fire Bird and technically Ice in her Woad Scout skin.)
I will update this whenever I remember another skin Idea I've had. Comments are appreciated.
AwsomeInventor1 votesfirst ZAC isnt getting bubble gum, Riot said so. second Cheshire cat Ziggs? maybe if its done right third, Doctor Zed. No. the Doctor Skins are reserved towards to ninjas that are good and not evil fourth Quinn? eah perhaps
Twilit Angel2 votesAww... lol. No Bubblegum Zac? Then perhaps they should just release Pool Party Zac. Just sitting in the background of another splash art until who knows when. Katarina, Garen, Darius?, Diana, Xin Zhao, Yorick?, Ahri, Jinx, Vayne, Lux, Morgana, Riven, Lulu, Gragas, Oriana, Nidalee, Ezreal, Aatrox, and some others were also seen in the pool party splash arts too. Maybe next summer we'll see some of them?
And I see why no for Zed, ah well. Plus I'd have to laugh at the Borderlands reference if they did do it. XD
Twilit Angel1 votesJust thought of something...
Drunken 
Idk what else to call it, but if anyone has played "Conker's Bad Fur Day," you should know what I'm talking about. Yes, Birdy, that drunk scarecrow at the beginning of the game. XD