JSFiddle - React, Tailwind, and code Playground

HTML

<div class="image-container">
    <img width="174" height="174" src="http://mysite.com/images/portfolio/p1.jpg" class="image-style" typeof="foaf:Image"/>
    <img width="174" height="174" src="http://mysite.com/images/portfolio/p2.jpg" class="image-style" typeof="foaf:Image"/>
    <img width="174" height="174" src="http://mysite.com/images/portfolio/p3.jpg" class="image-style" typeof="foaf:Image">
    <img width="174" height="174" src="http://mysite.com/images/portfolio/p4.jpg" class="image-style" typeof="foaf:Image"/>
</div>

JavaScript

$("div.image-container > img").each(function(index) {
    index = index + 1
    $(this).replaceWith('<div style="background-image:url(http://mysite.com/images/portfolio/p' + index + '.jpg)"><span>image</span></div>');

    alert(index + ' HTML is now changed to => ' + $("div.image-container").html());

});