I don't think I've seen mountains done in this style before. They look pretty good overall, but the part where they seem to ram right into that big lake and stop abruptly on it's shore looks totally unrealistic. Your rivers seem to have some points where they get super narrow or even completely discontinuous. The water looks fairly good, but gives the impression that it's deeper by the coasts and gets shallower out on the seas. The general convention is to use darker blue for deep water and lighter tones for shallow, but this is inverted in your map.