I know what you mean. I can't animate the actual change between the images - that's impossible.
But that is not what I needed. The change between all the source images should happen over fx. 1 second so that it shows each image within that timeframe and ends on the last one.
But I figured it out in the meantime - this is my code boiled down.
<div class="storyNumber" no="0"><img src=""></div>
function updateNumber() {
var no = $storyNumber.attr('no');
var $img = $storyNumber.find('img');
$img.attr('src', 'http://localhost/images/number_' + numberArray[no] + '.png');
}
var numberArray = [0, 127, 89, 80, 8, 200, 20, 87, 3];
var $storyNumber = $('.storyNumber');
TweenMax.to($storyNumber, 1.2, {
ease:Power4.easeInOut,
attr:{no:10}, roundProps:'attr',
onUpdate: updateNumber,
onComplete: function() { $storyNumber.attr('no', 0); }
});