Looking for a tutorial on how to digitally paint trees for my book cover, I stumbled upon a collection of excellent digital painting tutorials that cover things a little off the beaten path–like painting over photos to make backgrounds and color grading. They’re by Mclelun and you can see some of them here:

http://www.mclelun.com/p/tutorial.html

Click on the “Tutorial” tag link on that page to see all the helpful tuts!