You can use it like this:
$(document).ready(function(){
setTimeout("swapImages()",1000);
function swapImages(){
var active = $('.active');
var next = ($('.active').next().length > 0) ? $('.active').next() : $('#siteNewsHead img:first');
active.removeClass('active');
next.addClass('active');
setTimeout("swapImages()",1000);
}
});