Wow, cool looking formations, I really like it.
As for rivers just remember that water flows downhill and combines with other rivers to become one on it's way to the sea. It seldom if ever branches and if it does it soon comes back together. There is a link around here on "How to put rivers where they belong". The only thing I noticed and at the level I can zoom in I can't really tell it seems in some areas you have rivers running from one side of the continent to the other and then vice verse which could happen if the land actually slopes in opposite directions. I go by feel on these things but others here really get into the math.
Hubs of activity will be based on ease of transportation in most cases. It sounds like you have Seafarers so I would say your main cities will be coastal with decent harbor areas to keep ships safe from storms and so on. Just remember what people need to live and you should do alright with anything else. (ie, source of fresh water, fertile land, defensible locations when possible).
You don't have to have deserts but it's worth keeping in mind that mountains create their own weather so it's typical to find one side of a range greener than the other. Obviously if there is enough rainfall both sides can be lush. If you have strong winds from the Sea the trees can also be a bit wind battered and that might change the look of the forest from other places.
If you are using Photoshop the easiest way to upload a large image is to save as.. <.jpg> and lower the quality which does a pretty good job of keeping your details while shrinking the file size. Once you are inside of that 4.7mb limit go for it. I know I would like to be able to zoom in on this a tad more.