I had been typing a sizable response earlier today, but then my boss walked in and I quickly closed the page. Whoops.

I suggest some more brown and green tones in the mountains, specifically on the lower slopes, to make the peaks pop out a little more. The rivers should probably be a little slimmer, like Pasis suggested - certainly where they start in the mountains. Perhaps you could reduce the heavy black outline of the coast to something a little more subtle, and have that line continue stroking the shores of the rivers (possibly more subtle than the line on the coast). On that point, the rivers run into the black outline of the coast, so painting over those to make the river flow into the sea would look good.

Good work so far though, I'm looking forward to seeing you progress.