1. Start by opening a new file. I've used a small one in this example (about 250 x 150). Set the foreground color to a medium/light brown (#C8BE7E) and the background color to a light yellow (#F4F1DC)
Add a new layer, Shift+Ctrl+N. Make a selection with the Rectangular Marquee Tool and go to File > Render > Clouds. Do not deselect.
2. Go to the Channels palette
and Save selection as channel
(this will add an Alpha 1 channel). Deselect.
Go to Filter > Brush Strokes> Spatter... and set the Spray Radius to 10 and Smoothness to 5.
3. Ctrl + Click on the Alpha 1 channel to make a selection and go back to the Layers palette.
Select layer 1. Invers the selection Select > Inverse (Ctrl+Shift+I) and hit the Delete button on your keeboard.
Deselect.
4. Now for the last step.
Make sure you still have the same colors selected as in step 1.
Go to Filter > Sketch > Photocopy and set the Detail to 7 and Darkness to 8. If you are working on a larger canvas you might wanna try to use other settings.
That should do it!
More Tutorials: 
