I setup two Remote Desktop server for load balancing  in Windows Sever 2012 R2 and configured all – worked fine. I wanted to customise the Start Screen and did the steps as below from the support of multiple sites,

Step 1
Logged on using a test user and created the Start Screen as I wanted.

Step 2

The Start Screen binary appsfolder.itemdata-ms will be created in the path  %USERPROFILE%\appdata\local\microsoft\windows\ . Copied this file to the location on your RD Session Host Server(s): C:\Users\Default\appdata\local\microsoft\windows\appsfolder.itemdata-ms.

 

Step 3
Marked the file appsfolder.itemdata-ms as Read-only in the RD session host(s).

ReadOnly 

Step 4
Created a new OU – Remote Desktop Servers and placed the servers in the OU. Created a new GPO and linkeded to the OU that hosted to the RD Session Host servers. And create the following GPO Registry Preference.

image_registry

Key Path: Software\Microsoft\Windows\CurrentVersion\Run
Value data:: c:\windows\system32\attrib.exe %USERPROFILE%\appdata\local\microsoft\windows\appsfolder.itemdata-ms -R

What that does is it removes the read-only property of the appsfolder.itemdata-ms file inside the current users profile.

This allows the end user to customize his Modern UI Start Screen based on a Default Start Screen we pre-defined !

Source: http://microsoftplatform.blogspot.com.au/2012/11/predefining-and-customizing-modern-ui.html