Very well done build, island shape looks nice and sloping is good. Building quality and design also not bad.
Airport and wind turbines really are the main highlights of this build.
Work mainly has to be done on the tree coloration, variation (height, color, some design differences) and beach props. Just because you decide to dupe trees doesnt stop you from making multiple variations of it and dupe them around. I'm not talking about multiple species, I specifically mean similar designs but with different trunks, leaf pattern, etc. You also should work on your coloration; that dark green looks bad. Beaches need something to make them less perfect (ie clean)
Also might want to make another island w/o it being relatively flat.; short cliffs for sides work nice too.
If you're searching for good greens that are in Truenos I would suggest my own edit, found in the download pack for Althur. Probably self-promoting, but I think the colors I used would go very well for the trees here.