With the abundant amount of Seasonal items in the game, the idea of a seasonal tower comes to mind.
Having a separate "tower" just for the seasonal items adds new challenges for endgame player, but also allows newer players to earn advantages for collecting the multitude of seasonal goodies.
Two ways to make it different from the regular tower would be:
1) Only allow the seasonal tower to be accessible during its appropriate season.
2) Make it a Fortress!
The Tower only has one path and requires Mega Masteries to advance. Fortress is both wide and tall, showing all the seasonal items but also the level of mastery for each.
Have a graphic of a Fortress being built as the back drop. Make each of the Seasonal Items be a "Fortress Brick" and have them set side by side in a row. For every mastery tier you have, another brick is added to the appropriate column. Once you've reached MM in all the seasonal items, the bricks will now look like a solid Fortress Wall. Make it so the Fortress is visible on the user's profile to make it even more fun to complete.
As you complete the Fortress, you start to receive daily bonuses appropriate for the season. (E.g. extra frozen net during Winter that scale up with the Fortress completion)
A fun example: Frozen Fishing Fortress
