I’ll tell you how to represent nice wallpapers for the desktop.

Create a new file (File>New), that would have 1024x768 px and 72 dpi. We need to represent two rectangles with the usual Rectangle Tool (U)



We should apply the presented Blending Options>Gradient Overlay for the black upper layer.

 



Next we shall apply the below demonstrated Blending Options>Gradient Overlay for the lowest rectangle.

 



It’s the result that we have got at this moment:



Now we have to draw the clouds. It’s necessary to choose a filter on a new layer for this operation that may be found in this option - Filter>Render>Clouds.



Enter next this option Filter>Blur>Box blur