Very nice looking. I'm a tad conflicted about the coloring. Part of me really likes it and the other part wishes there was more contrast.

Shadows on the rivers may make them fit into the ground better. At the moment they seem to sit on top of the map. At least from up close. But before you go doing that they need to be moved around a bit. Rivers come together as they approach the ocean. They start at various places of high elevation and then merge before reaching the ocean. Think of a tree with its base on the coast and the ends of its branches in the mountains. You also have have several places where the rivers cross each other and flow uphill. This generally won't happen. There will typically be one lowest path and after the rivers meet they will both follow it. The same principle applies to lakes. There will be only one outflow or there will be none. I think your elevations/mountains are depicted very well so it might be effective to just pick random spots on your mountains and "inch by inch" judge where the next lowest elevation is. That should enable your rivers to merge naturally and having them conform to the elevation changes you've already drawn may also take care of that sitting on top thing I mentioned.