Concept art!? Pah, who needs it. It doesn't contribute anything directly to a project and just wastes the artists time.
Or so I used to think. However, I'm now coming round to the idea that it's a great way to engender interest and life into your programming project.
It's very hard to empathise with pages of code or small sprites, but concept art creates the world in which your game exists - in a way that you can actually see, rather than the original vision in your head which slowly fades away or gets distorted as the project fleshes out. The milieu is something that inspires people to continue working on a project long after the initial excitement has faded, and is a constant reminder of your projects original aim.