Very strong first piece! Keep it up.
One mistake that you made (that I always make) is that your sky's 2 orange colors are too similar to make out.
Secondly, the sun itself is casting quite a large reflection for its position in the horizon.
However, I really like how you did the island: nice shading and kudos on keeping it all 16 colors!
The island actually gave me the most trouble so I'm glad it turned out well.