I also did a nighttime image. First I added stars to the sky, Then used adjustment layers to first desaturate about 50%, next another adjustment layer -photo filter blue. Next, I again adjusted the hue/saturation followed more adjustment of brightness and contrast.
First I cropped the image and cloned out the leash and some background shadows. Then converted to B&W, followed by using split tone to to give it a sepia look, finally added some vignette.
I forgot to mention what I did for the picture above. Basically I cut the sailboat out of the original picture using PS CS6 and pasted it on to the image of sailboats in Sydney Harbor. I added waves and the wake using the clone tool to make the boat look likes it's moving in the water.