Add original photo for background.

Photo courtesy of a member in our cello section, obtained via Facebook.
Add background photo project.

Add the file to the project directory in the appropriate place, and
include the image in the project file itself.

The background image needs some *proper* optimising before going live
with this: it's currently ~2MB in size!
Begin the CGO styling proper.

Add the background image, fixed in position, attached to the body
element.

Add the semi-transparent background to a new "content" class, and apply
this class to both the page-header and the page body items. Starting to
look nice...