Removed ending php closing

Closing "?>" at end of functions.php may cause errors according to WordPress theme review 20513
Reorganizing custom header images

WP ticket 20513: "The header image intends to work as a logo. Hence, it needs to be disabled by default." To address this: (1) changed default image to ''; (2) set up register_default_headers so had place for previous default image; (3) added two other images I've created
Version 1.8.7