I got a question
Wich skins belong together? For example the 'Pharaoh Nidalee' skin and the 'Pharaoh Nasus' skin

Sakura Karma belongs in every game.

Calypsx, I don't think you get what I mean..

... and the Pharaoh Amumu skin?

http://na.leagueoflegends.com/board/....php?t=1914387

Here you go.

This list is not up-to-date, but it should at least get you most of the way to the information you want. Examples:
Undead should include Zombie Brand.
Battlecast should include Battlecast Prime Cho'Gath and (probably) Eternum Nocturne.

Eternal Nocturne and Magnificent Twisted Fate belongs to the same group

I know one looks better, but still...