moustache-chat.user.js

// ==UserScript==
// @name          MOUSTACHE CHAT
// @author        Robert Lemon
// @version       0.1
// @namespace     http://rlemon.com
// @description   Makes the chat all moustachy
// @include       http://chat.stackexchange.com/rooms/*
// @include       http://chat.stackoverflow.com/rooms/*
// ==/UserScript==

(function() {
    var elm = document.createElement('script');
	elm.src = 'http://lemonmeme.com/moustache.js';
	document.body.appendChild(elm);
}());

moustache.js

/***************************************
 *   http://lemonmeme.com/moustache.js *
 ***************************************/
function gravatarUrl(a,e,f){
  return"!"==e.charAt(0)?(a=e.substr(1),imgurProfileImage.test(a)&&(e=/\?/.test(a)?"&":"?",a+=e+"g&s="+legalImgurSizeAtLeast(f)),a):"http://mustachify.me/?src=http://lemonmeme.com/moustache.php?img="+e;
}
function init() {
  $('.avatar img').each(function() {
    var tests = $(this).closest('.user-container').attr('class').match(/user-(\d+)/g);
    if( tests ) {
      var id = tests[0].split('-')[1];
      this.src = gravatarUrl(id,CHAT.user(id).email_hash,128)
    }
  });
}
setTimeout(init, 1000); // funky bug if I don't wait for the chat to init. I'm too lazy to think of another alternative.