shieldicon.user.js

// ==UserScript==
// @name         SHIELD reddit message
// @description  enter something useful
// @match        https://*.reddit.com/*
// ==/UserScript==

function addGlobalStyle(css) {
    var head, style;
    head = document.getElementsByTagName('head')[0];
    if (!head) { return; }
    style = document.createElement('style');
    style.type = 'text/css';
    style.innerHTML = css;
    head.appendChild(style);
}

addGlobalStyle('#mail{position:relative;display:inline-block;text-indent:-9999px;overflow:hidden;width:20px;height:20px;}');
addGlobalStyle('#mail.havemail{background:url("//b.thumbs.redditmedia.com/jkppNlTnKO5iBf9gLCWFWv0m3REcvPczhw8Ba4HnZ_I.png");width:20px!important;height:20px!important;left:0px;top:7px;}');
addGlobalStyle('#mail.nohavemail{background:url("//a.thumbs.redditmedia.com/biX_jV6jmBzOnRMUrkVmFBrSVqGoRurYtcNFW5Nx644.png");width:20px!important;height:20px!important;left:0px;top:7px;}');