Create a Levels adjustment layer using a clipping mask to brighten and change the colour of the mountain background. Apply the following values shown below:
Then create a curves adjustment layer again in clipping mask to further enhance and brighten the scene.
After that apply a Hue/Saturation adjustment layer to desaturate the mountains slightly and blend in with the whole scene:
Now open Landscape stock, we will make that as our ground. Activate the free transform tool (Cmd/Ctrl+T) and enlarge it to fit it into the whole scene. Then give it a layer mask and mask away the part using a soft, low opacity brush (35-45%) as shown in the section below:
In clipping mask, create a Brightness/Contrast adjustment layer and set the brightness to +7 and contrast to +8 to brighten the ground and add a bit of contrast.
Then create a Vibrance adjustment layer, in clipping mask and set the vibrance to -22 to decrease it's vibrancy and make it a bit desaturated.
We will add a bit of shadow and lighting by applying Curves adjustment layers. Create the first Curves adjustment to darken the ground. Fill this layer mask with black by hitting Cmd/Ctrl+Backspace on the keyboard. Then using a soft brush 100% opacity, and with your foreground colour set to white and background colour to black as shown in the image below, reveal back the effects of the curves layer:
Now, create a second Curves adjustment layer to add a bit of brightness to the middle section of landscape. Refer the preview shown below:
Now that the main scene has been created, let's add some further details into the scene.
Open the cliff background stock and import it into the main canvas selecting only the cliff part and place it between the landscape and mountains' layers as shown in the preview below:
Then take the 'Cliff 2' stock and take the part shown in the selection in red colour and with clipping mask place it on the tip of cliff 1 and using the Warp Transform Tool, transform it as shown in the image below:
Then add a layer mask to it and using a soft brush of low opacity between 20-36%, mask the hard edges away.
Still on cliff 2 layer, hit Cmd/Ctrl+U on the keyboard to add a bit of Hue/Saturation to it:
Go to Layer > New Adjustment Layer > Levels and create a levels adjustment layer in clipping mask so that only the cliff gets affected and apply the values shown below for the blues channel:
Then create a Brightness/Contrast adjustment layer, decrease the brightness to -7 and increase the contrast +10:
Create a Levels adjustment layer and increase the highlights to add some lighting on the cliff's top. Fill it's layer mask with black, the same as we did in Step 6 and using a soft brush- 100% opacity and with the foreground colour set to white, reveal back the effects of the levels adjustment as shown in the selection below:
Create another Levels adjustment layer, this time for some shadowing. And following the same procedure with the previous Levels layer, fill the layer mask with black and using a soft brush (B) reveal back the effects as shown below:
Create a third Levels adjustment layer, in clipping mask and apply the following values to make the area of the cliff away from the lighting slightly darker. Follow the same procedure as you did with the other two levels adjustment above.