Change Wallpaper

<package
  id="bg"
  name="bg"
  revision="0"
  reboot="postponed"
  execute="once"
  priority="0"
  hidden="true">
    <install cmd='xcopy /Y "%WPKG%\custom\bg\bg.bmp" "C:\WINDOWS\web\wallpaper\bg.bmp"' />
    <install cmd='REG ADD "HKCU\Control Panel\Desktop" /v Wallpaper /f /t REG_SZ /d "C:\WINDOWS\web\wallpaper\bg.bmp"' />

    <!-- Use this apply it right away: RUNDLL32.EXE user32.dll,UpdatePerUserSystemParameters -->
    <!-- Otherwise it will take a logoff-login -->

</package>