Mask unnecessary part of the image. We will use the brightest part of the cloud as the main cloud texture.
Set this cloud layer to normal blending at about 40% opacity.
Duplicate (Ctrl+J) the cloud layer. Flip it horizontally and place the duplicate on the left side behind the building.
On this step, we will add more texture to the background. We will use the cosmos image for it. Open the image on the document. Place it above the cloud layer within the BG group.
Set this cosmos layer to soft light blending at about 87% opacity.
Then, give this layer surface blur filter by going to filter > blur > surface blur.
Type your instructions here.
Now create two new adjustment layers above the BG folder. Go to layer > new adjustment layers > brightness/contrast and gradient map.
Select gradient map layer and give it a layer mask. With a very soft round brush (0% hardness) set at low opacity at 15%, mask some areas indicated in red highlight.
Next, we should do color adjustments to the pirate house layer to match the background color. Open the pirate house group and select the layer. Create a new layer (Shift+Ctrl+N) with a clipping mask above the pirate house layer. On this layer, paint some soft shading with black on areas around the lower part of the building and some others.
Then, give this pirate house layer a new adjustment layer with a clipping mask. Go to layer > new adjustment layers > brightness/contrast.
Mask some parts around the building as indicated in red highlight. If we feel the value of the new adjustment layer is too much, we can lower the opacity of this layer a bit. With this value, set this layer to normal at about 87% opacity to have the result below:
Give more new adjustment layer: hue/saturation. Set this layer to normal at 100% opacity.
And another adjustment layer with a clipping mask: gradient map. Set this layer to soft light at about 40% opacity
Proceed to create horizon line for the scene. Create again a new layer behind the pirate house folder. Take a very soft round brush with opacity of about 20%. On this new layer, paint orange (#fe9703) horizon. Set this layer to color dodge. To make the line more subtle, we can give it a bit Gaussian blur filter accordingly.
Again create a new layer above the horizon layer, on this layer paint subtle orange color to add more color to the scene. Duplicate the new layer and play around with blending mode to get best result. As illustrated in the screenshot, we use hard light and linier light for the blending mode with set to the values accordingly.
Now create again a new layer below the horizon. On this new layer, paint soft yellow on the cloud. Set this layer to overlay at 100% opacity.
On this step, we will add distant rock to the scene. Create again a new layer (remember press Shift+Ctrl+N). On this new layer paint a dark rock shape as below.
With combination use of dodge and burn tool, paint highlight and shading on the rock to define dimension to the rock so it does not look flat:
Give this layer a layer mask and mask the lower part of it. Set this layer’s blending to normal at about 40% opacity.
Finally, give this layer color adjustment with a clipping mask. Go again to layer > new adjustment layers > hue/saturation. Check Colorize.