<script>
window.onload = function() {
    setTimeout(function(){ 
        var ForceLoadImages = document.createElement('script');
        ForceLoadImages.type = 'text/javascript';
        ForceLoadImages.src = 'link-to-the-script-to-force-load-images.js';
        document.body.appendChild(chatScript);
    }, 3000);
};
</script>

Solution - 1

so you mean you want to load images after 3 sec. once the page loads completely?

Solution - 2

From the example you showed it seems like they are loading a placeholder first then after load the actual image url is appended to the image tag https://jsfiddle.net/e2wkp9zh/ I did a quick fiddle on it, check it out, let me know if it works Monit

Solution - 3

Can you please share your webpage URL?

Solution - 4

oups... bad answer :)