Every time you load a new background update

html structure:

<div class="main"></div>

js:

function saveImg() {
	was imglens = 10;
	if (typeof(Storage) !== "undefined") {
	if (localStorage.imgPathcount) {
	localStorage.imgPathcount = Number(localStorage.imgPathcount) + 1;
	$(".main").css("background-image", 'url(img/' + localStorage.imgPathcount + '.jpg)')
	if (localStorage.imgPathcount>imglens) {
	localStorage.imgPathcount =1;
	$(".main").css("background-image", 'url(img/' + localStorage.imgPathcount + '.jpg)')
	}
	} else {
	localStorage.imgPathcount = 1;
	$(".main").css("background-image", 'url(img/' + localStorage.imgPathcount + '.jpg)')
	}
	} else {
	}
	}
	saveImg();