I took a class on narrative concept art through www.learnsquared.com. The teacher for the class is Jama Jurabaev who is not only an amazing concept artist, but also an incredibly nice person and excellent teacher. I really can't recommend this class highly enough if you're looking to pick up some new techniques and a deeper understanding of narrative concept art. This class put a lot more tools in my tool box and improved both the speed and quality of my work. Here's an example of one of images from my final assignment.