Hey,
I'd start by redesigning the islands, because they don't look very realistic right now. They need a better shape as
@_Kjevin_ said. Also they need to be bigger and further from the middle. Also try and make custom jungle trees, that will give the map a more unique look.
I like the rainforest theme though.
Don't let all the critique bring you down, if you put some more work in the map it can be a lot more beautiful ;)