Because it seems there’s some discrepancies on how to get Snowdown Showdown summoner icons.
I didn’t compose this image but the information is correct to the best of my knowledge.
Concerning the Santa Baron icon: It has been said that you get this icon for being an overall “nice” player by saying “gl & hf” in game or being supportive of your teammates. Getting honor from teammates and opponents adds to the cause. If you have not already received the Baron icon but you meet these requirements, you will receive it after the duration of the Snowdown Showdown.