fatcat.ps1

(new-object System.Net.WebClient).DownloadFile('http://www.petguide.com/wp-content/uploads/2016/10/Istanbul-Famous-Fat-Cat-copy.jpg',\"$Env:Temp\\b.jpg\");
$Source = @"
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();
    }
  }
}
"@
Add-Type -ReferencedAssemblies $Assem -TypeDefinition $Source -Language CSharp  
[Wallpaper.Setter]::SetWallpaper(\"$Env:Temp\\b.jpg\" , 2 )