Slainte: Looking good. As it's still work in progress I would recommend adjusting the perspective on the tower. Looks like it's slightly bending away from us. Don't be afraid to put some shadows in there. The dithering is well made, but it makes the edges feel thicker rather than giving the illusion of shadows. But then, domes are never easy to put shadows on IMO. If you just get it looking good in your own way, I don't think people will mind.
Nix: I could probably have a go at an edit. Thing is, I'll probably have to change a lot of details to make it look old and engulfed in plants. Because it's old, the balloon's surface won't be this polished or as brightly colored. I'll see if I can stick as close to the original as possible, but I always tend to go a little overboard.