That's a pretty good shot mate
I had a little go at touching it up for you. I used Paint Shop Pro X but I think the same method will apply to photoshop. Bear in mind that I was working from your resized image so the finished picture will show more artifacts than if I was using the full size image.
I first opened one of my archived shots of a sky scene in paint shop pro (psp). I resized that to the same size as your picture and saved it as a new image. I then opened your picture in psp and copied it by right clicking on the image and selecting copy. I then opened the the resized sky picture again and pasted the copy of your pic on top as a new layer.
As the sky in your picture was plain and bright, it made the next bit easy. I selected the bright areas using the magic wand tool and then used the eraser tool to erase those areas therefore exposing my sky shot underneath. Once done, I merged the layers into one picture. I then cropped the picture to remove parts of the top, right and bottom a bit before increasing the contrast and saturation a little. I then added a border and applied a little unsharp mask.