Overall it's really good. I'm always envious of the guys who make the nice first maps. (you should have seen some of my first attempts). I do have a couple of suggestions for you.
1.An outline around your landmasses would help them "pop" a bit more.
2. Your rivers look a bit like "rope" laid across the top of your land you could try a "bevel" filter on them. Also rivers at this scale would be about the same color as the shallower parts of your oceans (this is not technically realistic but it is a pleasing visual effect)
Your mountains and other terrain features look great. Are you planning on labeling this? Either way its a great first map.