Ah, another aspiring novelist drawn like a moth to the flame of cartography. Welcome, my brother! I have to say, your initial efforts are far, far superior to what I was cranking out a year ago. Your coastlines have a nice, organic roughness to them. The icons work well enough as placeholders, but consider trying your hand with the bezier tool in Inkscape to draw out some custom icons and porting them over. Really, though, I wouldn't worry about city icons until your terrain is where you want it.
Painting overhead mountains is a very tricky thing to get right. I've tried it a couple of times, with poor results, even with tutorials. Most drawn mountains around here tend to be isometric, or done with some cloud rendering and bump mapping (my preferred technique). I suggest you dig through the tutorial forum, look around, and try your hand at the techniques you find the most compelling.
Terrain-wise, I think you need a lot more texture variation. Climate is more than a single color in one area; each has its patterns and textures. Again, check out the tutorial section and give it a go with some small-scale stuff.
Your rivers are a bit odd in that they all seem to start in little round lakes. In one place, a river seems to split and head off in two very different directions. This doesn't happen in real life without a lot of human interference. It's all about the tributaries collecting water from their watersheds and feeding into bigger and bigger rivers, until you have a Mississippi, Amazon, Rhine, or Yang Tze.
Finally, the ocean color doesn't suggest water, and the detail in the texture seems a lot richer than the very plain-looking land. If anything, the water should look plain, and the land should look rich and textured. Water has been tricky for me; I've experimented with a variety of methods. My best results have incorporated some land glow effects with a subtle texture.
Most importantly, don't give up. you have a good sense of tectonics, mountain placement, and making a realistic coastline. I especially like the stripy islands in the east.
What's your novel about?