I'm a personal fan of floating islands, and this is a good take on the concept. My advise would be to try maintaining perspective when using many different images, the buildings in this piece are a bit askew to the horizon/sky and water. Maybe a different background would easily fix this. Also that boat on the right looks a bit funny, can't tell if it's falling or making its way up the waterfall, haha. Also i like the storm clouds and lighting you used on them, just a shame they are a tiny bit out of sync with the rest of the piece, perspective-wise. All things considered it's an enjoyable floating geographic picture