fix_gmail_images.user.js

// ==UserScript==
// @name           Fix gmail images
// @namespace      fixGmailImages
// @match https://mail.google.com/*
// ==/UserScript==
//
(function() {
    function fix() {
        var images = document.getElementsByTagName('img');
        for (var i = 0; i < images.length; i++) {
            var src = images[i].src;
            if (/.*googleusercontent.*#.*/.exec(src)) {
                images[i].src = src.split(/#/)[1];
            }
        }
    }

    var G_KEY_CODE = 71;
    document.addEventListener('keydown', function(e) {
        if (e.keyCode == G_KEY_CODE && e.shiftKey && e.altKey && !e.ctrlKey && !e.metaKey) {
            console.log('fixing images');
            fix();
        }
    }, false);
}());