You're looking for a combination of jQuery's XHR event handlers (for when the <img>
tag has been successfully inserted into the DOM), and a mechanism to detect when media themselves have been retrieved from the remote server.
There are at least two plugins you can use to perform the latter task. I suggest using them in combination with binding the required events from within the XHR event handler.
For example, with imagesLoaded, it'll probably look something like this:
$.ajax("url", function(data) {
var $html = $(data);
$('img', $html).load(function(e) {
// An image was retrieved
});
$('#targetContainer').append($html);
});