It's a good start, but I do have two points of feedback/critique:

- You have several rivers that split up to flow into different oceans. That's not going to happen, really, and you should probably fix this.

- Also, the underworld map looks like the continents are floating above caves that are the exact same size and shape as the continents. I am guessing it is just incomplete, but of course large caves need support, and as it stands those continents should just collapse and sink.