This is the image after I photoshopped the leaves in that I had shot separately. It's basically all using a photo of leaves and then adding a layer mask to fit it into the image. Sometimes also adding a curves layer to darken or brighten parts of the leaves helps to make it look realistic
Here I added a blurry background which I tried to match to the colors going on in the image with the model already. The color matching can be done in several ways. What I like to do is open up channels and then start with, say, green. This now displays a monochrome image where ONLY green color is shown. With this selected I add a curves layer to the image background (and only the background) and start tweaking the green curve. I look at the image and adjust the background until the image looks like the background fits in. Once this is done, do the same for red and blue. It takes some time but usually gives nice results.
Here I added some atmosphere by painting some smoke into the background and the foreground. You can do the same by photographing some smoke and blending it in. I tried to make some smoke using a mixture of glycerol and water (in a mix of about 1+6 or so) and putting it into a humidifier. This actually gives nice smoke but I probably need to find a more powerful humidifier given that the smoke just pours out of it more or less and I'd rather have it emmited a bit.
Now I added some color grading using a curves adjustment layer in order to make the shadows a bit colder and add a bit more punch. The curves adjustments are shown here:
Final touches. Here I decided to tone down the image a bit to not make it too saturated. In the end I actually made it a bit brighter again (see final image in the last post)
So I hope you found this in any way useful. Given that this year is approaching it's end I wish you a happy new year 2015- don't get too wasted on new year!