To address the confusion about who gets to choose the theme in the contest after the seasonal one:

The seasonal contests are set to always occur in March, June, September, and December.

The winner of a contest prior to a seasonal contest month chooses the theme for the month after the seasonal contest.

February chooses April;

May chooses July;

August chooses October;

November chooses January.

This is how it looks, in order:

January winner chooses February theme
February winner chooses April theme
March is Seasonal contest for Winter
April winner chooses May theme
May winner chooses July theme
June is Seasonal contest for Spring
July winner chooses August theme
August winner chooses October theme
September is Seasonal contest for Summer
October winner chooses November theme
November winner chooses January theme
December is Seasonal contest for Autumn

The Seasonal contest winners don't have to choose a theme --and because they don't-- they can enter the next Seasonal contest.

Winners who do choose a theme don't get to enter that contest because, presumably, it's an unfair advantage. Those restrictions are in the rules.

So there you have it!