Hey Max, thank you for the feedback =)
Let me see

a) Highlights the mountains? As in making them lighter? I actually did the inverse: the higher the darker...

b) For the few rivers issue: yes, I knew this. It's because being a world map, I want to show only the most important things, the main mountains, the main forests: all the minor things are left out. But I think I should add more rivers. May you tell me the problems with the rivers you say? Like, some rivers being misplaced, lakes, etc?

c) Thanks for letting me know about the deserts' color.

merci beaucoup ^^