<div id='parent'>
     <img src="blabla">
     <img src="blabla">
     <img src="blabla">
</div>
var el = document.getElementById("parent");
var checkCount = el.getElementsByTagName("img").length;
function onCheck() {
     checkCount--;
     if(checkCount <= 0) {
        el.removeEventListener("load", onCheck, true);
        el.removeEventListener("error", onCheck, true);
        console.log("complete");
     }
}

el.addEventListener("load", onCheck, true);
el.addEventListener("error", onCheck, true);