var aktiv;
var counter = 1;
var pics;

function newPicture()
{
  document.getElementById("headerbild").src = pics[counter];
  counter++;
  if(counter >= pics.length)
  {
    counter = 0;
  }
}

function startHeaderChange(i, pictures)
{
  pics = pictures;
  aktiv = window.setInterval("newPicture()", i);
}