function mimemail_extract_files($html) {
  $pattern = '/(<link[^>]+href="?|<object[^>]+codebase="?|@import |src="?)\/?([^"]+)("?)/emis';
  $html = preg_replace($pattern,'"\\1". _mimemail_file("\\2") ."\\3"', $html);
  
  $document = array(array(
    'Content-Type' => "text/html; charset=utf-8",
    'Content-Transfer-Encoding' => 'base64',
    'content' => chunk_split(base64_encode($html)),
  ));
  
  $files = _mimemail_file();
  
  return array_merge($document, $files);
}

background: url(/themes/swietakrowa/images/tlo_graf.jpg)
background: url('/themes/swietakrowa/images/tlo_graf.jpg')
background: url("/themes/swietakrowa/images/tlo_graf.jpg")

background: url (/themes/swietakrowa/images/tlo_graf.jpg)
background: url ('/themes/swietakrowa/images/tlo_graf.jpg')
background: url ("/themes/swietakrowa/images/tlo_graf.jpg")

zeby zamienialo tak samo jak
<img src="/themes/swietakrowa/images/tlo_graf.jpg" />