Banner Location Guide / Snowfall Challenges
The Season 7 Week 6 secret Snowfall Banner can be found where the crown of RVs is, far south of Paradise Palms.
To actually get the banner to appear though, you first need to complete SIX sets from any of the weekly challenges (weeks 1-10).
Once any of them has been completed, this secret banner can be collected and the challenge "Find the Secret Banner in Loading Screen #6" will appear in the Snowfall Challenges. It will reward you with a banner to equip to your profile.
Completing 60 weekly challenges will unlock the secret snowfall skin.