$csCode = @'
//https://social.msdn.microsoft.com/Forums/en-US/0d4737a9-639c-4648-b437-6fcbaee5c2ae/how-do-i-set-the-wallpaper-background-image-per-desktop-monitor?forum=csharpgeneral
//https://devblogs.microsoft.com/oldnewthing/20140314-00/?p=1503
//https://stackoverflow.com/questions/334630/opening-a-folder-in-explorer-and-selecting-a-file/334645
//https://github.com/catwalkagogo/CW.Win32/blob/master/CW.Win32/Shell/ShellItemArray.cs

using System;
using System.Runtime.InteropServices;

public class Wallpaper{
    IDesktopWallpaper pDesktopWallpaper = null;
    IShellItemArray ppsiItemArray = null;    

    public Wallpaper()
    {
        pDesktopWallpaper = (IDesktopWallpaper)(new DesktopWallpaperClass());
    }

    [StructLayout(LayoutKind.Sequential)]                                 
    public struct RECT                                                    
    {                                                                     
        public int left;                                                  
        public int top;                                                   
        public int right;                                                 
        public int bottom;                                                
                                                                          
        public RECT(int left, int top, int right, int bottom)             
        {                                                                 
            this.left = left;                                             
            this.top = top;                                               
            this.right = right;                                           
            this.bottom = bottom;                                         
        }                                                                 
    }
    
    [ComImport()]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [Guid("b63ea76d-1f85-456f-a19c-48159efa858b")]
    public interface IShellItemArray
    {
    }
    
    [ComImport()]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [Guid("43826D1E-E718-42EE-BC55-A1E261C37BFE")]
    public interface IShellItem
    {
    }
    
    [ComImport]
    [Guid("B92B56A9-8B55-4E14-9A89-0199BBB6F93B")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    interface IDesktopWallpaper
    {
        HRESULT SetWallpaper([MarshalAs(UnmanagedType.LPWStr)] string monitorID, [MarshalAs(UnmanagedType.LPWStr)] string wallpaper);
        HRESULT GetWallpaper([MarshalAs(UnmanagedType.LPWStr)] string monitorID, [MarshalAs(UnmanagedType.LPWStr)] ref string wallpaper);
        HRESULT GetMonitorDevicePathAt(uint monitorIndex, [MarshalAs(UnmanagedType.LPWStr)] ref string monitorID);
        HRESULT GetMonitorDevicePathCount(ref uint count);
        HRESULT GetMonitorRECT([MarshalAs(UnmanagedType.LPWStr)] string monitorID, [MarshalAs(UnmanagedType.Struct)] ref RECT displayRect);
        HRESULT SetBackgroundColor(uint color);
        HRESULT GetBackgroundColor(ref uint color);
        HRESULT SetPosition(DESKTOP_WALLPAPER_POSITION position);
        HRESULT GetPosition(ref DESKTOP_WALLPAPER_POSITION position);
        HRESULT SetSlideshow(IShellItemArray items);
        HRESULT GetSlideshow(ref IShellItemArray items);
        HRESULT SetSlideshowOptions(DESKTOP_SLIDESHOW_OPTIONS options, uint slideshowTick);
        [PreserveSig]
        HRESULT GetSlideshowOptions(out DESKTOP_SLIDESHOW_OPTIONS options, out uint slideshowTick);
        HRESULT AdvanceSlideshow([MarshalAs(UnmanagedType.LPWStr)] string monitorID, DESKTOP_SLIDESHOW_DIRECTION direction);
        HRESULT GetStatus(out DESKTOP_SLIDESHOW_STATE state);
        HRESULT Enable(bool benable);
    }
    
    public enum DESKTOP_WALLPAPER_POSITION
    {
        DWPOS_CENTER = 0,
        DWPOS_TILE = 1,
        DWPOS_STRETCH = 2,
        DWPOS_FIT = 3,
        DWPOS_FILL = 4,
        DWPOS_SPAN = 5
    }
    
    public enum DESKTOP_SLIDESHOW_OPTIONS
    {
        DSO_SHUFFLEIMAGES = 0x1
    }
    
    public enum DESKTOP_SLIDESHOW_STATE
    {
        DSS_ENABLED = 0x1,
        DSS_SLIDESHOW = 0x2,
        DSS_DISABLED_BY_REMOTE_SESSION = 0x4
    }
    
    public enum DESKTOP_SLIDESHOW_DIRECTION
    {
        DSD_FORWARD = 0,
        DSD_BACKWARD = 1
    }
       
    [ComImport, Guid("C2CF3110-460E-4fc1-B9D0-8A1C0C9CC4BD")]
    public class DesktopWallpaperClass
    {
    }
    
    public enum HRESULT : int
    {
        S_OK = 0,
        S_FALSE = 1,
        E_NOINTERFACE = unchecked((int)0x80004002),
        E_NOTIMPL = unchecked((int)0x80004001),
        E_FAIL = unchecked((int)0x80004005)
    }

    [DllImport("shell32.dll", SetLastError = true)]
    public static extern void SHParseDisplayName([MarshalAs(UnmanagedType.LPWStr)] string name, IntPtr bindingContext, [Out] out IntPtr pidl, uint sfgaoIn, [Out] out uint psfgaoOut);
    
    [DllImport("shell32.dll", SetLastError = true)]
    public static extern int SHCreateShellItemArrayFromIDLists(int cidl, IntPtr[] rgpidl, out IShellItemArray ppsiItemArray);
    //===========================================================================================================================

    public void SetSlideshow(string folderPath)
    {
        uint psfgaoOut;
        var ptrList = new IntPtr[1];
        SHParseDisplayName(folderPath, IntPtr.Zero, out ptrList[0], 0, out psfgaoOut);
        SHCreateShellItemArrayFromIDLists(1, ptrList, out ppsiItemArray);
        pDesktopWallpaper.SetSlideshow(ppsiItemArray);
    }

    public void SetSlideshowOptions(uint shuffle, uint milliseconds)
    {
        pDesktopWallpaper.SetSlideshowOptions((DESKTOP_SLIDESHOW_OPTIONS)shuffle, milliseconds);
    }

    public void SetWallpaper(string filePath)
    {
        string monitorID = null;
        pDesktopWallpaper.GetMonitorDevicePathAt(0, ref monitorID);
        pDesktopWallpaper.SetWallpaper(monitorID, filePath);
    }

    public void SetPosition(uint position)
    {
        pDesktopWallpaper.SetPosition((DESKTOP_WALLPAPER_POSITION)position);
    }

    public string GetWallpaper()
    {
        string monitorID = null;
        string filePath = null;
        pDesktopWallpaper.GetMonitorDevicePathAt(0, ref monitorID);
        pDesktopWallpaper.GetWallpaper(monitorID, ref filePath);
        return filePath;
    }

    public void Enable(bool benable)
    {
        pDesktopWallpaper.Enable(benable);
    }

    public uint GetSlideshowOptions()
    {
        DESKTOP_SLIDESHOW_OPTIONS options;
        uint slideshowTick;
        pDesktopWallpaper.GetSlideshowOptions(out options, out slideshowTick);
        return slideshowTick;
    }

    public uint GetStatus()
    {
        DESKTOP_SLIDESHOW_STATE state;
        pDesktopWallpaper.GetStatus(out state);
        return (uint)state;
    }
}
'@


Add-Type -TypeDefinition $csCode
$o = [Wallpaper]::new()

設定桌布

$o.SetWallpaper('C:\new\img0.jpg')

設定桌布(幻燈片)

$o.SetSlideshow('C:\picFolder')

#第一個參數：0 按照順序;  1 打亂順序
#第二個參數：圖片變更間隔 milliseconds
$o.SetSlideshowOptions(1, 10000)

其他設定

#顯示方式
#0:CENTER; 1:TILE; 2:STRETCH; 3:FIT; 4:FILL; 5:SPAN
$o.SetPosition(0)

#0:關閉桌布; 1:啟用桌布
$o.Enable(0)

別的設定桌布方法

$Pic = "C:\new\img0.jpg"
$FolderPath = Split-Path  $Pic
$FileName   = Split-Path  $pic  -Leaf

$Shell = new-object -com "shell.application"
$File = $Shell.NameSpace($FolderPath).ParseName($FileName)

	#WallpaperStyle
	#並排	0		而且TileWallpaper要設  1
	#置中	0
	#延展	2
	#全螢幕	6
	#填滿	10
Set-ItemProperty 'HKCU:\Control Panel\Desktop' -Name "WallpaperStyle" -Value "0"
Set-ItemProperty 'HKCU:\Control Panel\Desktop' -Name "TileWallpaper" -Value "0"

$File.verbs()   |  ?{  $_.name -like  "*(&B)"  } | %{ $_.doit()   }

# For 英文版 Windows
#$File.verbs()   |  ?{  $_.name -like  "Set as desktop &background"  } | %{ $_.doit()   }

sleep 2

參考資料：
How do I set the wallpaper / background image per Desktop / Monitor?
How do I create an IShellItemArray from a bunch of file paths? - The Old New Thing
c# - Opening a folder in explorer and selecting a file - Stack Overflow
CW.Win32/ShellItemArray.cs at master · catwalkagogo/CW.Win32 · GitHub