I'm very much pleased that, you've taken my critiques positively! I hope to see you participating in the May 2009 Challenges, but, keeping my critiques in mind! Those who learn from their mistakes, are bound to succeed!
Well, in digital matte-painting, most of the times real photo reference images are used to create a matte-painting, since the ultimate aim of a Digital Matte-Painter is to create a photo-realistic digital matte-painting! You can use that photo reference directly in your matte-painting, to add a touch of realism to it, provided, you have taken permission from the photographer, to use it in your matte-painting!