We've so far had two different "seasonal" models of PokeStops. There were the Valentines ones that got released in 9.1.3, and there were the Pride ones that got released in 9.1.5. Since seasonal PokeStops models are a thing Pixelmon seems to like to do, I figured all the variants could remain in the files. Rather than adding them in a version and removing them in a later version (which resulted in the Valentines variants getting used for way longer than Valentines season), we could just set them to automatically switch to the variants during a certain time period, similar to those present-textured chests that replace all the Minecraft chests from December 24-26th. It also means that the modelers' and texturers' hard work doesn't have to get removed in later versions.
We can make the date ranges for the seasonal PokeStops be configurable, which would be nice since holidays and things like Pride are sometimes celebrated at different times in different countries.