Cool map! However a few tips and things I noticed:
-The water is a nice touch, however, it looks a little messy, you could layer it, by adding different layers of glass under one another, and making the one layer less random. You could also lower it a whole block so it looks more realistic.
-The underneath of the islands could be smoothed out a little, instead of using the same color as the top of the island perhaps a rocky andesite and cobblestone layers could be nice? Additionally, I think the team colors could be represented by a long fence post line with wool to make it look like multiple banners. (Kind of what you have going on in the middle)
-For the middle, it feels a little underwhelming. The theme is market, so it would be nice to maybe see some stands with items, and things like that. What you have now is ok, but it needs to feel a little more alive and "interactable" if you understand my meaning.
-The final thing I'll mention for aesthetics is the trees. I don't know which type of tree you are aiming for however, the current trees look a little droopy like a willow. I'd recommend trying to make palm trees. They would require the leaves to be a bit more springy and the tree itself to be taller and less hunched. I'd also recommend changing the biome if possible to jungle to make the leaves more colorful.
-Gameplay-wise the main issue I have is the map is too small. The generators, shop, and spawn take away a lot of building space, in addition, PVP may be difficult or annoying as the islands are just too small. The half middle is fine, and the middle is a little all over the place. While I like you can travel up and down areas with relative ease, you'd want the players to use this in certain situations, the main focus should be the generators and the combat on the ground, running all around could cause stalls and be sometimes annoying for players.
Overall, nice build, but it could use some work! If you would like assistance or more advice I would be more than happy to help! <3