This is just my personal taste, so in not any way is my advice going to be the same to others...probably.

Here goes:
Did you had in mind of making your coastline squarish?
Since it looks a bit unrealistic per se.
But the islands are awesome, though
I couldn't make islands like that for $100 xD

Why not add more details, like roads, rivers, mountains and the sort?
Makes the map more beautiful to look at.

Good job and keep up the good work.