You might try 2 of the free Photoshop-compatible plugins from this site. Namely, "Ilustrator" and "Line Art." Perhaps not quite what you're looking for, but the price is right, they are easy to use, and  playing with the sliders can give a variety of different looks.

http://www.xero-graphics.co.uk/freeware.htm

Here's an image I made with by playing with the Illustrator plug-in for about 2 minutes. Again, probably not what you're looking for, but it may give you an idea of what's possible:

http://excalibur.renderosity.com/mod/gallery/index.php?image_id=1252899&member

 

Gallery