Show loading gif while image is loading

I made some code where the user can upload some images from a zip. On the next page I need to show all the images seperatly in a 85*85 px frame.

The problem is that it may take some time for all the images to load. So I want to show a loading gif while the user waits for the image to load.

I've set the src of the images to be the loading gifs, while I created some checkboxes with the real source as id

echo "<td><img src=\"beelden/ajax-loader-black-16.png\" id=\"img".$image."\" style=\" width: 85px; height: 85px; border: 1px solid gray; background-color: #fff; padding: 10px;\">";
echo "<input type=\"checkbox\" id=\"img[".$image."]\" name=\"check_image[]\" value=\"".$filename."\" /></td>";
<input type="hidden" name="aantal" id="aantal" value="<?=$image?>" >

Then I created some javascript to check if the image is loaded, and when it is, it is supposed to replace the source of the image.

<script>
    var aantal = document.getElementById("aantal").value;
    for(var i = 0; i < aantal; i++){
        var source = document.getElementById("img["+i+"]").value;
        var img = new Image();
        img.onload = function(){
            $("#img"+i).attr('src', source);
        }();
        img.src = source;
    }
</script>

But this does not work the way I expected, I think it fires for all of the images as soon as the first one is loaded. Any ideas what I am doing wrong or how to fix this?