2nd display should show the same background as login/lock screen:

chrome/browser/resources/chromeos/login/screen_account_picker.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview Account picker screen implementation.
  */
 
 cr.define('login', function() {
   /**
@@ skipping 152 matching lines @@
    * @param {boolean} enabled Whether Caps Lock is on.
    */
   AccountPickerScreen.setCapsLockState = function(enabled) {
     $('pod-row').classList[enabled ? 'add' : 'remove']('capslock-on');
   };
 
   /**
    * Sets wallpaper for lock screen.
    */
   AccountPickerScreen.setWallpaper = function() {
+    // TODO(antrim): remove whole method once 136853 is accepted.
+    return;
     var oobe = Oobe.getInstance();
     if (!oobe.isNewOobe() || !oobe.isLockScreen())
       return;
 
     // Load image before starting animation.
     var image = new Image();
     image.onload = function() {
       var background = $('background');
 
       // Prepare to report metric.
@@ skipping 11 matching lines @@
     };
     // Start image loading.
     // Add timestamp for wallpapers that are rotated over time.
     image.src = 'chrome://wallpaper/' + new Date().getTime();
   };
 
   return {
     AccountPickerScreen: AccountPickerScreen
   };
 });