svg file header image not displaying

Example

1. set default header image

2. override default header image using below filter

add PHP code to functions.php

<?php
add_filter('raindrops_header_image_background_image', 'my_background' );

function my_background($background) {

	$background = 'background: url( http://your-svg-image/tiger.svg);';
	return $background;
}
?>

result

http://www.tenman.info/wp3/manualraindrops/files/svg-header-image.jpg

Thank you.