1. File > New
6" x 6", resolution 72

2. Color palette.

Click on Foreground color swatch.

Choose a medium brown.

3. Click on Background swatch.

Choose a light tan color.

4. Filter > Render > Clouds

5. To apply the same action multiple times, we are going to use Actions palette.
Window > Actions
Click on New Action
Then click Record.

6. Filter > Render > Difference Clouds

7. Stop recording the action.

8. Apply this action about 17 times by pressing "play" button:

This is what it looks like.

9. Create a new layer

10. Replace the Background color with darker one.

11. Filter > Render > Clouds

12. Use Difference Clouds action about 24 times.

13. Rename the layer "dark".

Mode: Multiply.

Opacity: 12

14. Image > Adjustments > Levels:

Black 19, Gamma 1, White 70

15. Duplicate Background layer

Mode: Overlay. Opacity: 51

16. Image > Adjustments > Invert

17. Edit > Transform > Flip Horizontal

18. Edit > Transform > Flip Vertical

19. Create a new layer

20. Set default colors.

21. Filter > Render > Clouds

22. Layer mode: Overlay. Opacity: 32

23. Actions palette.

Run Difference Clouds action about 4 times for a rougher look.

24. Image > Adjustments > Levels

Gamma 1.4

Output Levels: 17 and 255

25. New layer. Name it "color"

Mode: Color. Opacity: 20

26. Choose warm Foreground and Background colors.

27. Filter > Render > Clouds

28. In Actions palette run Difference Clouds about 12 times.

What do you think?