The image you create should be high resolution with the same size and scale as the one above. There should also be light-colored space in the image to allow the heading text to be clearly visible. The heading text is not a part of the image, it is text overlayed in the html code.
Our first idea was to bring in some of our photos of our office building and add in a background. Obviously, this looks very amateurish, but at least you can get an idea of the direction we were thinking: http://dev.plazaoffices.com/ . We are open to new ideas though.
The image you create should match the style of the template mentioned above. I am attaching images of our office that you may or may not want to use in the image you create. The image should fit the site for all popular screen sizes (wide desktop, normal desktop, tablet, mobile).