The custom header graphic needs to be quite wide and I do not have a photo that closely matches the aspect ratio. I ended up cropping a photo that I liked. I took this on a trip to Pittsurgh recently. It was shortly after sunrise, a time of day that I am not very familiar with. The cropped image is a bit more ominous looking than the full image. The brigher sky and the clouds tinted with the sunrise are cropped out int he header.
I will have to look for opportunites to take a photo that matches the aspect ratio that I need.