[Reflection.Assembly]::LoadWithPartialName(“System.Windows.Forms”)

$t = (Get-ChildItem ENV:USERPROFILE).Value
$fi = $t + "\pepe.png"
$fo = $t + "\pepe.bmp"
$b = [Text.Encoding]::Unicode.GetBytes($fo)
$b += 0,0,0

(new-object net.webclient).DownloadFile('https://i.imgur.com/TrymOlU.png', $fi)
(new-object System.Drawing.Bitmap($fi)).Save($fo,"BMP")
Remove-Item -Path "$($env:APPDATA)\Microsoft\Windows\Themes\CachedFiles" -Force -Recurse -ErrorAction SilentlyContinue
Remove-Item -Path "$($env:APPDATA)\Microsoft\Windows\Themes\TranscodedWallpaper" -Force -ErrorAction SilentlyContinue
Set-ItemProperty -path 'HKCU:\Control Panel\Desktop\' -name TranscodedImageCache -value $b
Set-ItemProperty -path 'HKCU:\Control Panel\Desktop\' -name wallpaper -value $fo
rundll32.exe user32.dll, UpdatePerUserSystemParameters