Step 1Create a new document / image with the size of your desktop (if you are unsure what size your desktop is then just press the PrtSc (Print Screen) button on your keyboard and Photoshop will automatically set the correct size! Handy tip there!)
Step 2Make sure your colours are reset (Foreground - Black and Background - White) by pressing 'D' on your keyboard. And create a new layer.
Step 3Now make some clouds by going to Filter -> Render -> Clouds
Step 4Now add "plaster" to the clouds by going to Filter -> Sketch -> Plaster. Leave the settings to their default selection.
Step 5Now we'll need to add a Motion Blur to it. So Filter -> Blur -> Motion Blur (Angle: 90, Distance: 999)
Step 6Finally to add our finishing touch to it, right click the new layer and goto Blending Options and goto Gradient Overlay and use the following settings.
There you go and it should look very nice. (Like mine!)