Exclusive Icon

http://na.leagueoflegends.com/en/news/game-updates/player-behavior/instant-feedback-powers

"To celebrate positive play, every player who hasn’t been chat/ranked restricted or banned over the last three months will unlock an exclusive summoner icon. You can expect that to land in your account by 5.19." -League of Legends

Posting this for people who have questions about the unknown icon