I have a couple geographical questions to consider. And please feel free to correct me (anyone) for I am not in any even tiny way a geographer--just a guy who likes art and maps.
First, are there enough rivers and water to support such a lush area as is depicted? Normally, this sort of place will have many, many, many both justifying the "green" and explaining where the rain goes that supports it. This will depend upon the scale, of course, but judging from your moutnains and such it seems a valid question.
Also, you have lakes fed by rivers, but no other outlets. This is, of course, possible, but without odd/unique circumstances, won't river-fed lakes overflow into streams and such running into the sea. (I pose this question mainly because I live by the Great Lakes, but I am unsure and will do some checking).
I really must compliment you on your mountain texture; it is one of the few cases in which I really, really like the use of PS's powers in this regard: they look very believable and not like big crumpled pieces of papers or chiseled blobs. But, you include no other elevations, such as hills, valleys, and such. It seems highly unlikely to me that there would be mountains on flat plains (though, of course, it's possible.)
Finally, I agree with the others that the color choices are about 10% too bright. I like how vibrant things are, but this is just a hair's breadth over the edge, IMO.
I hope these questions--even if completely rejected by you--were at least a tad helpful. You have a nice style. I likey!