Set the current Windows wallpaper to Bing's image-of-the-day

Set-BingWallpaper.ps1

$ErrorActionPreference = 'Stop'
if ((Test-Path "$PSCommandPath.autoupdate") -and ! (Test-Path "$PSCommandPath.config")) {
    Set-Content "$PSCommandPath.config" '{ "autoupdate": true }'
    Remove-Item "$PSCommandPath.autoupdate"
}
$config = Get-Content -Raw "$PSCommandPath.config" -ea Ignore | ConvertFrom-Json
cd ~
if (! (Test-Path -PathType Container Wallpapers)) { mkdir Wallpapers }
cd Wallpapers
$last = Get-ChildItem *.jpg, *.jpeg | Sort-Object LastWriteTime -Descending | Select-Object -First 1
if ($last -and [datetime]::Now - $last.LastWriteTime -lt '6:00:00') {
    exit
}
while (! (Test-Connection 1.1 -Count 1 -Quiet)) { Start-Sleep 1 }
if ($config.autoupdate -and $args[0] -ne '-noupdate') {
    $gistid = '1306bbd9d42bb93af59c7bbcb2a243ad'
    $gistfn = 'Set-BingWallpaper.ps1'
    $gist = Invoke-RestMethod https://api.github.com/gists/$gistid
    if (([datetime]$gist.updated_at).ToUniversalTime() -gt (gi $PSCommandPath).LastWriteTimeUtc -and $gist.files.$gistfn.truncated -eq $false) {
        Set-Content $PSCommandPath $gist.files.$gistfn.content
        & $PSCommandPath -noupdate
        exit
    }
}
$today = (Invoke-RestMethod 'https://www.bing.com/HPImageArchive.aspx?format=js&n=1').images[0]
if (! $today) {
    Write-Error 'HPImageArchive API returned no results'
}
if ($today.startdate -notmatch '^(\d{4})(\d\d)(\d\d)') {
    Write-Error "Unexpected image startdate: $($today.startdate)"
}
$fn = ($Matches[1,2,3] -join '-') + '.jpg'
$url = 'https://www.bing.com/' + $(if ($config.urlbase_suffix) {
    $today.urlbase + $config.urlbase_suffix
} else {
    $today.url
})
Invoke-WebRequest $url -OutFile $fn
$setwallpapersrc = @'
using System.Runtime.InteropServices;
public class Wallpaper {
    public const int SetDesktopWallpaper = 0x14;
    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 int SetWallpaper(string path) {
        return SystemParametersInfo(SetDesktopWallpaper, 0, path, UpdateIniFile | SendWinIniChange);
    }
}
'@
Add-Type -TypeDefinition $setwallpapersrc
if ([Wallpaper]::SetWallpaper("$PWD\$fn") -eq 0) { Write-Error 'SystemParametersInfo() returned false' }
Get-ChildItem *.jpg, *.jpeg | Sort-Object CreationTime -Descending | Select-Object -Skip 14 | Remove-Item
if ($today.copyright -and (Get-Command New-BurntToastNotification -ea Ignore)) {
    $common = @{Silent = $true; UniqueId = 'SetBingWallpaper'; AppLogo = '\null.jpg'; wa = 'SilentlyContinue'}
    if ($today.copyright -match '(.*)\((\u00a9.*)\)') {
        New-BurntToastNotification -Text $Matches[1] -Attribution $Matches[2] @common
    } else {
        New-BurntToastNotification -Text $today.copyright @common
    }
}

This should work in either Windows Powershell 5.1 (pre-installed on Win10+) or Powershell 7+. JPGs are saved in a Wallpapers subdirectory at the script's location (up to 14 days' worth, older ones are deleted). The default download resolution is (currently, Microsoft can change this) 1920x1080. To choose a different one, create a JSON config file named Set-BingWallpaper.ps1.config and place it in the same directory as the script. E.g. for 3840x2160, the config file should contain:

{ "urlbase_suffix": "_UHD.jpg" }

Here are the available urlbase_suffix settings:

"_UHD.jpg"       # 3840x2160
"_1920x1200.jpg"
"_1920x1080.jpg"
"_1366x768.jpg"
"_1280x768.jpg"
"_1024x768.jpg"
"_800x600.jpg"
"_800x480.jpg"
"_768x1280.jpg"  # Portrait orientation
"_720x1280.jpg"  # Portrait orientation
"_640x480.jpg"
"_480x800.jpg"   # Portrait orientation
"_400x240.jpg"
"_320x240.jpg"
"_240x320.jpg"   # Portrait orientation

You can also enable auto-update mode (as in auto-update the script, not the wallpaper; use Task Scheduler to run the script daily), though it's not recommended unless you really trust this Internet stranger:

{ "autoupdate": true, "urlbase_suffix": "_UHD.jpg" }

If the BurntToast PowerShell module is installed, a notification annotating the image is displayed.