Hey there! :3

So firstly, your terrain.
It's all water. As much as sometimes this idea can work, I don't think it does on this plot. And that's because you dont have an appropriate amount of land for the structure to be built on. You have a little bit of sand, but the area you've given it is so small, the water takes over - it means it's no longer relevant. If you had the area under the tower bigger, spreading wider, with more than one layer and block type, it'd be a whole lot better.
You could also detail the water and the island edge with things like lily pads, wheat, reeds etc. Be creative!

Secondly, organics. You don't have any. You can get away with not having any organics on the plot, but it's always nice to have one or two. The most common kind of organic is a custom tree - you could have one coming off the edge of the island, if you made the island out of grass for example.
Another idea of an organic is an animal - maybe you could fill some of the water space you have on your plot with a whale, or a dolphin. Whatever you choose! :3

Lastly, your structure. I'm not too sure of the relevance of the spheres, but I like the little Sunfury sign on the side, it's a nice little touch, just cause yolo right?
But onto the main aspect of the plot; the tower.
It's a good start. You have a nice shape and a good starting palette - now you need to add to it!
Some depth; adding layers to the building so it's not flat.
Some detail; adding details like stairs/slabs to make the building more pleasing to look at.
More palette; more block variety than just stonebrick. This can be to add to the detailing, or it can be to make it look prettier :D I'd suggest some coloured clay blocks if you're going with stonebrick.

Good luck!
- Dutty :3