Few thoughts. First, there are some inconsistencies in line width. The line work on your mountains and forests is thin and clear and looks pretty nice all around. The line stroke surrounding the island/continent on the other hand is large, fuzzy and pixalized. It looks rather odd. The line stroke along your rivers is thin but barely visible. I'd consider trying to make these lines more consistent; try redrawing the coastline with a pen of the same px size as that which you drew the mountains. Also, make the lines along the shores of the rivers much more apparent.

Second, I find the transition of water color and style from rivers to ocean odd. I think you would do better to pick one style and be consistent with it. My suggestion would be to go with the a solid color for the ocean, perhaps with a lighter hew for the shallower water surrounding the land. You could play around with layer blending modes to try to get the parchment texture to be visible as well.

Finally, there are some inconsistencies in color and texture within the land. Most of your land is covered with a grey-green texture but there are these textureless bright green splotches dispersed within it. These, quite frankly, are an eyesore. This is due to the fact that they both lack any texture, and are bright in comparison to their surrounding. Try to work on making these blend in a bit better by adding texture and muting the brightness a bit.

On the plus side, I like your mountains, forests and city markers. I think there is potential here.

Cheers,
-Arsheesh