The champions and the skins are the following:
Alistar
Amumu
Annie+ Annie in Wonderland
Ashe
Blitzcrank+ Boom Boom Blitzcrank
Darius
Dr. Mundo
FiddleSticks
Gankplank
Garen
Gragas
Jax
Kassadin+ Festival Kassadin
Kayle
Kindred
Lee Sin+ Muay thai Lee Sin
Malphite
Master Yi
Nasus+ Infernal Nasus
Nautilus
Nunu
Olaf
Pantheon
Poppy+ Ragdoll Poppy
Rammus
Rek'Sai
Renekton
Ryze
Shaco
Shen
Shyvana
Singed
Sion
Sivir
Skarner
Soraka
Taric
Teemo
Tristana
Trundle
Tryndamere
Twisted Fate
Udyr+ Spirit Guard Udyr+ Definitely Not Udyr
Veigar+ Final Boss Veigar
Volibear+ Runeguard Volibear
Warwick
Xin Zhao