Oh hey you're the guy who asked me questions about map submission, I was waiting for your creation :>
First, I think the theme you used is very creative and unique, I like it.
Now let's analize the map closely:
The starting islands: To be honest, I don't get why you decided to go for a house with a garden, I'd have surely made something cave/mine themed. Here are some pictures of what I mean:
The sub-middle islands: They are pretty small for an 8 players map and the slabs you put in there aren't pvp friendly, they'd be pretty annoying. I'd suggest you to give them a more interesting shape (Not just a straight line) and try to add more details (Not too many), it looks empty as it is right now: you could add some rocks or maybe a sort of rail, it's up to you.
The middle island: As for the sub-middle islands it is too small and a bit too empty: You could add some more grounds to it to make the gameplay more interesting and unusual.
The islands at the sides: I strongly suggest you not to make pixelart of in game textures since they aren't very good. If you want to make a picaxe you could make a custom one, here a couple of pictures of a picaxe I built in the past (it would be quite big for your build but it's just to give you an idea of what I mean:
And also those small islands are pretty far from the mid, I don't know if people would spend time to build there just to get diamonds since 8v8 is usually a fast game.
So, that being said, I like the theme of the map since it's something we don't see very often but I think the build could've been done better.
Cubecraft has very high standards for its maps and we always search for maps with an unique style. that's why it can't be used right now.
If you want to follow the tips I gave you and improve your build, maybe you'd have higher chances to get added.
I strongly appreciate the time you spent building a map for us and I hope to see other creations by you :>
Good luck!