First time we got this question, most people seem to like it.

There is no config setting in AL to do that but maybe it is just enough to remove the BGInfo.exe from the LabSources folder. Or you disable BGInfo after the deployment:

Invoke-LabCommand -ComputerName Client1 -ScriptBlock {
    Remove-Item -Path C:\Windows\bginfo.*
    Set-ItemProperty -Path 'HKCU:\Control Panel\Desktop' -Name 'WallPaper' -Value ''
}