Summoners Rift if permanently stuck in Spring, I think it wouldn't be that hard to make a Summer skin map, Autumn skin map & Winter skin map. You could literally change the season according to the region. I think it would make the game some what less repeatable and more enjoyable.
Rioter comment about how reskining SR takes a colossal amount of effort.
The regional color balance of the map would make this very difficult. The color palette was something they worked very hard on when redesigning the new Summoner's Rift last season, and they did a fantastic job. This is not to say that they could not come up with an alternative skin which could work just as well to accomplish what you are requesting, but I definitely understand why it is not readily available.
