Mr. Lake has been kind enough to provide tutorials on the making of photo-realistic textures, albeit they are photoshop-centric.
http://www.conxort.com/mrlake/mainpage.php (Scroll down)
If you don't like what you do at first, redo it. Any artist will tell you that. Many of the paintings hanging in the Louvre and other art museums around the world have been painted over "mistakes" and jpegs and targa's are infinitely cheaper than canvas and oil paint.