The climate and rivers thing is really just a nitpick, it's your world so the logic of it is up to you

Just a question though, is the green outline along the desert rivers because they have a narrow fertile zone, like the Nile? Makes sense. Only other criticism is the transition between biomes eg desert and grassland is a little sharp - if you browse Google Earth these naturally blend a bit more.
Also, the rivers, are they all Wilbur generated? You do have a lot of them in the north and they're very uniformly wiggly, rivers tend to be so wiggly on very flat land, less wiggly further inland, though if its a big flat swampy region that would make sense.