JavaScript code:

// ==UserScript==
// @name     WaffleImages Fixer
// @version  1
//
// @include [url]https://forums.somethingawful.com/*[/url]
// ==/UserScript==

function getNewUrl(url) {
  var match = url.match(/http:\/\/img\.waffleimages\.com\/([0-9a-fA-F]+)\/.+\.([a-zA-Z]+)/);
  if (match) {
    var hash = match[1];
    var extension = match[2].substring(0, 3).toLowerCase();
    return `[url]https://randomwaffle.gbs.fm/images/[/url]${hash.substring(0, 2)}/${hash}.${extension}`;
  } else {
    return url
  }
}

document.querySelectorAll('img[src^="http://img.waffleimages.com"]').forEach((elem) => {
  elem.src = getNewUrl(elem.src);
});

document.querySelectorAll('[href^="http://img.waffleimages.com"]').forEach((elem) => {
  elem.href = getNewUrl(elem.href);
});