Requested Check Over
I structured it rather oddly, but it'll do
Not having a lot of water to conserve file size shouldn't be stressed. Those hunting for templates would be helpful for that demographic. But it all depends on what your vision of the map is an how you can improve it. So I won't go and call for radical change.
Back to the actual aesthetic of the map. It's a tidy looking one, but it simply is too small for people to care for. If a map was this size and has top notch quality, it would be rated high. But for now, your map's quality aesthetically wise isn't acceptable.
The way you used water and water doodads in this map does not look pleasant to the eyes for most I'd predict. It's too much of depressed feeling contrast. If you notice, there are a handful of barrens themed maps, not only templates, that change the water color. While blizzard usually keeps the color, they also keep barrens maps... well more barren than other type of maps. You don't have the barrens feeling in this map, especially with the vibrant sunken ruin trees, flowers, etc. I personally suggest you go one way or the other, that being a barren map or a lushes map. Changing the water color would be the first step.
Secondly, the doodad placement was only sub-par. Of course I'm not suggesting to spam it or make it extravagantly impressive (unless you have the effort to!), but to simply add more one by one that fit. A wise man once told me, decorate your map like your decorating your mothers house. If you don't think you could add more, downloading custom doodads and applying them appropriately might be your best bet in getting hire ratings. Places you an add doodads are near and on the boundary areas of the map, in the open water, and simply around other doodads to complement them. I don't recommend you add some in the open areas you intended you leave open.
Thirdly, I suggest you smooth your shores a bit more for a more blended look. Right now it almost seems like humans built these islands by dumping chunks of land in designated areas. The tile variation was fine all around. I don't think it can get too much better.
Good luck on your map, this stays as rejected for now.