This should fix the problem in bug #37 where background images do not show. This is happening because the css property 'background-image' only accepts a 'url()' value. (http://www.w3schools.com/cssref/pr_background-image.asp)
Change made on line 27 from
$bg_image_css = ! empty( $image ) ? 'background-image: url( '. esc_url( $image ) . ' ) no-repeat top center;' : '';
to
$bg_image_css = ! empty( $image ) ? 'background: url( '. esc_url( $image ) . ' ) no-repeat top center;' : '';
