Try adding:
function my_custom_header_setup() {
add_theme_support( 'custom-header', apply_filters( 'my_custom_header_args', array(
'default-text-color' => 'fff',
'width' => 540,
'height' => 160,
'flex-height' => true,
'wp-head-callback' => 'twentyfourteen_header_style',
'admin-head-callback' => 'twentyfourteen_admin_header_style',
'admin-preview-callback' => 'twentyfourteen_admin_header_image',
) ) );
}
add_action( 'after_setup_theme', 'myn_custom_header_setup' );
function twentyfourteen_admin_header_style() {
?>
<style type="text/css" id="twentyfourteen-admin-header-css">
.appearance_page_custom-header #headimg {
background-color: #000;
border: none;
max-width: 540px;
min-height: 160px;
}
#headimg h1 {
font-family: Lato, sans-serif;
font-size: 18px;
line-height: 48px;
margin: 0 0 0 30px;
}
#headimg h1 a {
color: #fff;
text-decoration: none;
}
#headimg img {
vertical-align: middle;
}
</style>
<?php
}
endif;
to your child theme’s functions.php file.,