Nothing that technically difficult. Mostly color correction, adjust brightness (dark on one side, light on the left), dodge and burn to tie it all together. The house and the roof is slightly warped to fit together. I used stroke on the pen tool to make the lines for the ballon and then added some bevel and emboss to create some more body to them.

For the texture on the house I used some of the gnomes leg.

From the very beginning I thought where I wanted my lightsource to come from (left side). The difficult part was finding a nice sky without the sun present.

The key is to find sources the can match the light in your imagined picture. Don't chose a source with a conflicting lightsource because it will make it very hard to blend it properly.

The trees can be hard to blend in the edges, but I simply masked it out roughly and then dottet the edges of the mask with a standard brush to simulate the leaves.

On the base of the chimney and the balcony I used the smudge tool to make a nice transition between the leg and the other items because the leg is so much smoother in the texture.

I hope you like it :)