Looks good for a first go, but yeah...those rivers... To me it looks more like long fiords instead of rivers. Even carved out of the mountains. I think the bevel on the rivers is something to look at. I am not a PS user so I am no help there. I do like the rest of it though. I agree with AS that the mountains can work as is, and the colors and and water texture also work.

Oh and by the way, Welcome to the Guild and have some rep for posting a Map along with your first post.