複数の url を順番に処理していく https://github.com/ariya/phantomjs/blob/master/examples/render_multi_url.js

urls.js

var Lwp, urls;

var urls = [
  'http://qiita.com/',
  'https://github.com/',
  'http://www.yahoo.co.jp/'
];

Lwp = function(urls, callbackPerUrl, callbackFinal){
  var next, page, retrieve, urlIndex, webpage;
  urlIndex = 0;
  webpage = require("webpage");
  page = null;

  next = function(status, url){
    page.close();
    callbackPerUrl(status, url);
    return retrieve();
  };

  retrieve = function() {
    var url;
    if(urls.length > 0){
      url = urls.shift();
      urlIndex++;

      page = webpage.create();

      page.open(url, function(status) {
        if (status === "success") {
          page.render('list_' + urlIndex + '.png');
          next(status, url);
        }else{
          next(status, url);
        }
      });
    }else {
      callbackFinal();
    }
  }

  retrieve();
};

Lwp(urls,
  function(status, url){
    console.log(url);
  },
  function(){
    phantom.exit();
  }
);