Download and set the wallpaper from hexdsl.co.uk

hexdslwallpaper.ps1

# Change to image1 if you fancy a different wallpaper.
Invoke-WebRequest -Uri https://hexdsl.co.uk/image2.jpg -OutFile wall.jpg

# Pinched from Stackoverflow :-)
$setwallpapersrc = @"
using System.Runtime.InteropServices;

public class Wallpaper
{
  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)
  {
    SystemParametersInfo(SetDesktopWallpaper, 0, path, UpdateIniFile | SendWinIniChange);
  }
}
"@
Add-Type -TypeDefinition $setwallpapersrc

[Wallpaper]::SetWallpaper((Get-Item .\wall.jpg).fullname)