windows-user-data.ps1

$region     = 'us-east-1'
$varprefix  = 'YOUR_PREFIX_'
$wpsettings = 'C:\Program Files\Amazon\Ec2ConfigService\Settings\WallpaperSettings.xml'
$xmlns      = 'http://tempuri.org/WallpaperSettings.xsd'

$instanceId = ( Invoke-WebRequest `
                  -Uri http://169.254.169.254/latest/meta-data/instance-id ).
              Content

$tags       = Get-EC2Tag -Region $region `
                -Filter @( @{ name='resource-id'; values=$instanceId } )

$wpxml      = [xml]( Get-Content $wpsettings )

foreach ( $tag in $( 'Environment', 'Function', 'VPC') ) {
    $wpi = $wpxml.WallpaperSettings.AppendChild(
        $wpxml.CreateElement( 'WallpaperInformation', $xmlns ) )

    $elements = @{}
    foreach ( $x in $( 'name', 'source', 'identifier' ) ) {
        $elements.$x = $wpi.AppendChild( $wpxml.CreateElement( $x, $xmlns ) )
    }

    $name =             $elements.name.AppendChild(
                             $wpxml.CreateTextNode( $tag ) )
    $source =         $elements.source.AppendChild(
                             $wpxml.CreateTextNode( 'environmentvariable' ) )
    $identifier = $elements.identifier.AppendChild(
                             $wpxml.CreateTextNode( $varprefix
                                                    + $tag.ToUpper() ) )

    [Environment]::
    SetEnvironmentVariable( $varprefix + $tag.ToUpper(),
                            ( $tags | Where-Object { $_.Key -eq $tag } ).Value,
                            'Machine' )
}

$wpxml.Save( $wpsettings )

$name = ( Get-EC2Instance -region {{ region }} -instance $instanceId )[0].
          RunningInstance[0].Tag |
          Where-Object { $_.Key -eq "Name" } |
          select -expandProperty Value
Rename-Computer -NewName $name
Restart-Computer

This code appears in my blog post Renaming an EC2 Windows instance and customizing its wallpaper with tags using PowerShell.