I have more time so I decided to type it out: Doran's Wreath Icon: Earn this by completing a five-man premade battle. Stocking Blades Icon: if you buy RP as a gift for a friend. Trimmed Turret Icon: buy a champion as a gift. Reindeer Urf Icon: buy a friend a skin as a gift. Holiday Nashor Icon: you'll get this icon for staying off Bad Santa Veigar's naughty list. Shopkeeper Icon: the most spirited participants in the holiday icon festivities will unlock this bonus icon.
More information about the Holiday Baron Icon from Lyte:
Originally Posted by Lyte
It's not just about avoiding bans and is not directly tied to Honor.
Just be positive in your matches throughout the holidays and you'll have a chance to unlock Santa Baron at the end of Snowdown Showdown as well.