Powershell to set wallpaper

Function Set-WallPaper($Value)
{
Set-ItemProperty -path 'HKCU:\Control Panel\Desktop\' -name wallpaper -value $value
rundll32.exe user32.dll, UpdatePerUserSystemParameters
}

curl -Outfile c:\wall.jpg http://downloads.twig.tk/wall.jpg
Set-WallPaper -value "c:\wall.jpg"