Try something like this:
var counter = 0;
var images = ["Assets/BGImages/head_sandwichman2.jpg", "Assets/BGImages/head_sandwich.jpg", "Assets/BGImages/head_pizza.jpg"];
function setBackground(){
counter++;
var selector = counter % 3; //assuming you have 3 images to slide through
var image = 'url("' + images[selector] + '")';
$('.global-header').css('background-image', image);
setTimeout(setBackground(),3000); //every 3 seconds change the image
}
$(document).ready(function() {
setTimeout(setBackground(), 3000); //start sliding 3 seconds after the page finished loading
});
Please take care with this solution as it's late over here and I can't test it anymore. There are more elegant solutions for sure.