The trees are fine. Yes, they are as tall as the mountains. So what? They're graphical symbols. This map is clearly not trying to be a picture and bigger trees mean you have to draw fewer of them, which makes it less work for the cartographer. It looks good, too. What I would consider changing is the glow on the text. It seems a bit much, especially on "Land of the Prydonians". I think with the limited colors you are using, the text could stand out all right without any glow at all, really.