Christmas - Patches of snow and snow flakes falling from the sky. maybe a snowman and presents in the courtyard
Halloween - darker lighting, pumpkins, candles, and leaves scattered
Valentines - Brown/yellow trees and "heart banners"
st patricks day - clovers, rainbows, and pots of gold!
And we can include some "Seasonal" challenges in the clockworks
Actually, I'm in line with this suggestion. It reminds me of PSO, whenever there were certain holidays, the lobby would change! God I miss that game...