After winning The Season 2 World Championship held in early October of 2012 in Los Angeles and taking the $1,000,000 prize pool home, Taipei Assassins get a special honor from Riot and receive their own skins for some of their favorite champions.
Soon everyone will be able to play the champions that TPA used for winning the championship with their new special skins. As it appears from the wallpaper the champions that get special skins are: Shen, Mundo, Oriana, Ezreal and Nunu.

Taipei Assassins managed to win The Season 2 World championship after a victory over Azubu Frost in the finals.
Source - League of Legends