Trello Board Bing Wallpaper GreaseMonkey UserScript

I occasionally use Trello for maintaining tasks for projects. It helps me stay on task and estimate completion times better. The interface makes managing/creating/completing tasks very easy. It is a breath of fresh air for task management.

I thought it would be cool to see a different background everyday. So decided to use the Bing wallpaper rss feed to get me an amazing image every day.

The GreaseMonkey script below works in Firefox. I have tested it in Chrome (via TamperMonkey) and there are a couple issues. I will try to resolve them and update it here.

// ==UserScript==
// @name        Trello Board Canvas Bing Image
// @namespace   net.intellectualponderings.TrelloBoardCanvas
// @require     http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js
// @grant       GM_getValue
// @grant       GM_setValue
// @grant       GM_log
// @grant       GM_xmlhttpRequest
// @grant       unsafeWindow
// @include     https://trello.com/b/*
// @version     1
// ==/UserScript==

GM_xmlhttpRequest({
    url: "http://feeds.feedburner.com/bingimages",
    dataType: "xml",
    //data: "",
    //type: "GET",
    method: "GET",
    //success: function (data){
    onload: function (responseObject){
        var data = responseObject.responseText;
        GM_log(data);
        var enclosures = $(data).find("enclosure"), // /rss/channel/item/enclosure[url]
            imgurl = $(enclosures[0]).attr('url'); //alert(imgurl);
        $(".board-canvas").css({ 
            'background': 'url(' + imgurl.replace("http://", 'https://') + ') no-repeat center center', 
            'background-size': '100%;'});
    },
    //Error: function (XMLHttpRequest, textStatus, errorThrown) {
    onerror: function () {
      // Same code as in my question...
    }
});