Is it for a child, or a more adult party? A two tier with fall leaves and maybe berries would look good?
AYou could make winter theme on the top and fall the bottom tier. Connect with a water fall running down from the top where the water is frozen with thick ice and still flowing below. Lots of red, brown, orange leaves on bottom tier and almost empty trees, bending to the side from the wind have a snowman on top of the cake, blowing down on the tier below.
Or do a total "season hack"
Turkey with candy canes.
Pilgrim with Christmas caps.
Pumpkins with bows on top.
White leaves with blue highlights and glitter and brown/ yellow orange marbled snowflakes.
thanks! all great ideas!