(new-object System.Net.WebClient).DownloadFile('https://pbs.twimg.com/media/DvSImELUcAE31OH.jpg',"$Env:Temp\b.jpg");

Add-Type @"

using System;

using System.Runtime.InteropServices;

using Microsoft.Win32;

namespace Wallpaper

{
public enum Style : int
{

Tile, Center, Stretch, NoChange
} public class Setter {

public const int SetDesktopWallpaper = 20;

public const int UpdateIniFile = 0x01;

public const int SendWinIniChange = 0x02;

[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]

private static extern int SystemParametersInfo (int uAction, int uParam, string lpvParam, int fuWinIni);

public static void SetWallpaper ( string path, Wallpaper.Style style ) {

SystemParametersInfo( SetDesktopWallpaper, 0, path, UpdateIniFile | SendWinIniChange );

RegistryKey key = Registry.CurrentUser.OpenSubKey("Control Panel\\Desktop", true);

switch( style )

{

case Style.Stretch :

key.SetValue(@"WallpaperStyle", "2") ;

key.SetValue(@"TileWallpaper", "0") ;

break;

case Style.Center :

key.SetValue(@"WallpaperStyle", "1") ;

key.SetValue(@"TileWallpaper", "0") ;

break;

case Style.Tile :

key.SetValue(@"WallpaperStyle", "1") ;

key.SetValue(@"TileWallpaper", "1") ;

break;

case Style.NoChange :

break;
}

key.Close();

}
}

}

"@

[Wallpaper.Setter]::SetWallpaper("$Env:Temp\b.jpg" , 2 )