Duplicate this layer and make it about 50% smaller.
Next step is to create nice light rays. Create new document, with square size (width = height), and width is about 200% of your original image width. (if you design wallpaper at 1024x768, create 2000x2000 image). Fill it with any color, and in Layer effects, check Gradient Overlay. Open dropdown list of gradient selection, select Noise family of gradients, and select any noise gradient. Then, set Style to Angle.
To convert Layer effect to editable image, flatten image (from Layer menu). Desaturate (Ctrl-Shift-U).
Crop image as shown here. Example: if entire image with gradient is 2000x2000, crop to 1024x768.
Copy all (Ctrl-A, Ctrl-C) and paste into our original image.