$url = "WALLPAPER URL HERE"

$ext = $url.split(".")[-1]

$wp = "$Env:USERPROFILE\Desktop\---wp.$ext"

iwr $url -O $wp

Function Set-WallPaper {
 
param (
    [parameter(Mandatory=$True)]
    # Provide path to image
    [string]$Image,
    # Provide wallpaper style that you would like applied
    [parameter(Mandatory=$False)]
    [ValidateSet('Fill', 'Fit', 'Stretch', 'Tile', 'Center', 'Span')]
    [string]$Style
)
 
$WallpaperStyle = Switch ($Style) {
  
    "Fill" {"10"}
    "Fit" {"6"}
    "Stretch" {"2"}
    "Tile" {"0"}
    "Center" {"0"}
    "Span" {"22"}
  
}
 
If($Style -eq "Tile") {
 
    New-ItemProperty -Path "HKCU:\Control Panel\Desktop" -Name WallpaperStyle -PropertyType String -Value $WallpaperStyle -Force
    New-ItemProperty -Path "HKCU:\Control Panel\Desktop" -Name TileWallpaper -PropertyType String -Value 1 -Force
 
}
Else {
 
    New-ItemProperty -Path "HKCU:\Control Panel\Desktop" -Name WallpaperStyle -PropertyType String -Value $WallpaperStyle -Force
    New-ItemProperty -Path "HKCU:\Control Panel\Desktop" -Name TileWallpaper -PropertyType String -Value 0 -Force
 
}
 
Add-Type -TypeDefinition @" 
using System; 
using System.Runtime.InteropServices;
  
public class Params
{ 
    [DllImport("User32.dll",CharSet=CharSet.Unicode)] 
    public static extern int SystemParametersInfo (Int32 uAction, 
                                                   Int32 uParam, 
                                                   String lpvParam, 
                                                   Int32 fuWinIni);
}
"@ 
  
    $SPI_SETDESKWALLPAPER = 0x0014
    $UpdateIniFile = 0x01
    $SendChangeEvent = 0x02
  
    $fWinIni = $UpdateIniFile -bor $SendChangeEvent
  
    $ret = [Params]::SystemParametersInfo($SPI_SETDESKWALLPAPER, 0, $Image, $fWinIni)
}


Set-WallPaper -Image $wp -Style Fill