Ok, so i'm not an experienced builder, but I'll throw my opinion in here anyways. I don't know if you have just started building this map or if this is finished or whatever, but I have to be honest - This map doesn't look great, sorry :c
The colours of redstone, yellow and light blue, and then leaf green all clash together - try to remove a couple it might help.
The leaf structure you have is interesting, but i don't think the glowstone belongs there either,and it could use a bit more detail. Try adding some log struts here and there or something like that. I like the beacon, but again i don't really understand the theme or why it is there! xD Is it supposed to be a temple or something idek o.O
I like some parts of the floating island, the purple glass with nether brick looks good but again i feel there's too much stuff clashing together! There are those magma block thingys (forgot the name of them) with mossy cobble and then a stone floor - I don't understand what the theme is! The islands look better than mid though.
Try to make it so the islands are not flat underneath, it makes them a lot more interesting to look at. I would also suggest you try to round things off a bit more. I know this is a game based around squares but not everything has to be blocky and uniform xD try rounding off the corners of the water pool and your floating island and it should be a lil easier on the eye.
If you would like help building, pm me and if i'm available I'll give you a helping hand!
Above all, keep working on it! Don't let my comments dishearten you, they are just a silly old dragon's opinion : P
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