Setting the lock screen background with PowerShell

There's no simple Registry value holding the path to the image used as the lock screen background for a given user (not counting the policy one that only works on Enterprise/Education). To automate setting the current user's lock screen background, you can use PowerShell!

Add-Type -AssemblyName System.Runtime.WindowsRuntime
$asTaskGeneric = ([System.WindowsRuntimeSystemExtensions].GetMethods() | ? { $_.Name -eq 'AsTask' -and $_.GetParameters().Count -eq 1 -and $_.GetParameters()[0].ParameterType.Name -eq 'IAsyncOperation`1' })[0]
Function Await($WinRtTask, $ResultType) {
 $asTask = $asTaskGeneric.MakeGenericMethod($ResultType)
 $netTask = $asTask.Invoke($null, @($WinRtTask))
 $netTask.Wait(-1) | Out-Null
 $netTask.Result
}
$tStorageFile = [Windows.Storage.StorageFile,Windows.Storage,ContentType=WindowsRuntime]
$img = Await ([Windows.Storage.StorageFile]::GetFileFromPathAsync($path) $tStorageFile
[Windows.System.UserProfile.LockScreen,Windows.System.UserProfile,ContentType=WindowsRuntime] | Out-Null
[Windows.System.UserProfile.LockScreen]::SetImageFileAsync($img)

The Await function used here appeared previously on this blog -- it allows PowerShell code to await and get results from WinRT tasks. The rest of the script is a straightforward application of the relevant WinRT APIs. First a StorageFile is opened from the $path specified, then it's used to set the lock screen image.