Photoshop Madness

We'll start by creating a new canvas (Ctrl+N) 500x100 px. Select as your foregroung colour a dark shade of blue and white as your backgroun colour. Now use Filter-> Render-> Clouds.Use Ctrl+J on that first layer to copy it onto a new layer. Then use Filter->Render-> Difference Clouds. Use Image -> Adjustments-> Levels and move the midlle grey slider to the left until you achieve the lightning effect.
Use Ctrl+I on the difference cloud layer to invert it. Then use Ctrl+J again to copy that onto a new layer.
Use Filter-> Pixelate-> Mosaic with a 15 cell size square on the third layer. After that use Filter-> Brush Strokes -> Accented Edges with 3 edge width, 40 edge brightness and 4 smoothness. Use the Overlay blending mode on the third layer, then merge it with the second layer by selecting it then using Ctrl+E.
On the second layer use Overlay blending mode then merge it with th
Use Image -> Adjustments -> Levels to darken the image a bit by selecting the black slider and dragging it to the right.