They could do anything related to spring. Flowers of all kinds, bright colors, cherry blossoms which is big in Japan, the equinox. It doesn't have to be a holiday most of the seasonals aren't tied to a holiday to begin with just tied to a time of year or they just decided to do that theme that month. I prefer the seasonals that aren't tied to holidays because they are just more fun. They call it a 'spring" banner not an Easter banner and every year it being only bunnies annoys me, same with the winter banner.