Finally I made it work with following codes.
<div id='ajax_cf' class='ContentFlow'>
<div class='flow'> </div>
<div class='scrollbar'><div class='slider'><div class='position'></div></div></div>
<input type="button" value="get images!" onclick="getPictures();" />
var ajax_cf = new ContentFlow('ajax_cf');
function addPictures(){
var ic = document.getElementById('itemcontainer');
var is = ic.getElementsByTagName('img');
for (var i=0; i< is.length; i++) {
ajax_cf.addItem(is[i], 'last');
}
}
function getPictures() {
for (var i=0; i<15; i++ ){
$("#itemcontainer").prepend("<img onclick='' class='content' src='contentflow/pics/pic0.png'/>");`
}
addPictures();
}