I think everyone has done a 4-seasons picture by now. I suppose I'm just following the fold :) Each of the seasons were drawn individually, then placed together so they flow into one another (and yes, that's all the same tree...I got lazy, sorry :P)
I've done about 3 versions of winter by now, but I can't stand how any of them have come out, so the series isn't finished yet. Oh, but it shall be someday!
Drawn from scratch in Photoshop.