var $j = jQuery.noConflict();
$j(document).ready(function(){
  function showRandomImage(size) {
    var randNo = Math.floor(Math.random() * 17);
    if (size==1) {
      $j('#header').css({'background-image': 'url(http://www.malte-reiter.de/fileadmin/templates/img/header/background-1-'+ randNo +'.jpg)'});  
    } else {
      $j('#header').css({'background-image': 'url(http://www.malte-reiter.de/fileadmin/templates/img/header/background-4-'+ randNo +'.jpg)'});    
    }
  }  
  if(window.location.pathname == '/' || window.location.pathname.match('home')) {
    //1000px 
    showRandomImage(1);
  } else {
    //400px  
    showRandomImage(4);
  }
});