1. Create a new document and fill the background layer with black. For this step, I've created an 800x600 pixels document. Press the D key on your keyboard to ensure that the default foreground (black) and background (white) colours are being used.
2. In the Actions pallet (Alt+F9), create a new action.
3. With the action recording, duplicate the current layer and change the blending mode of the new layer to screen.
4. Add a Clouds filter (Filter> Render> Clouds).
5. Add a Mosaic filter (Filter> Pixelate> Mosaic) with a cell size of 50 square.
6. Apply a Reticulation filter (Filter> Sketch> Reticulation) with the following properties:
Density: 0
Foreground Level: 50
Background Level: 0
7. In the Actions pallet (Alt+F9), stop recording the action.
8. Play the previously created action about 7-10 times until your screen has been filled with tiles.
9. Link all of the layers except for the background and merge (Ctrl+E). Photoshop CS2 users may simply select multiple layers and Merge (Ctrl+E).
10. Apply a Photocopy filter (Filter> Sketch> Photocopy) with the following properties:
Detail: 24
Darkness: 1