How can I use the images within shell32.dll in my C# project?

You can extract icons from a DLL with this code:

public class IconExtractor
{

    public static Icon Extract(string file, int number, bool largeIcon)
    {
        IntPtr large;
        IntPtr small;
        ExtractIconEx(file, number, out large, out small, 1);
        try
        {
            return Icon.FromHandle(largeIcon ? large : small);
        }
        catch
        {
            return null;
        }

    }
    [DllImport("Shell32.dll", EntryPoint = "ExtractIconExW", CharSet = CharSet.Unicode, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    private static extern int ExtractIconEx(string sFile, int iIndex, out IntPtr piLargeVersion, out IntPtr piSmallVersion, int amountIcons);

}

...

form.Icon = IconExtractor.Extract("shell32.dll", 42, true);

Of course you need to know the index of the image in the DLL...

This thread on the MSDN developer forums offers a solution:

The typical way to implement these in .NET is to use the graphics provided in the ZIP file located at C:\Program Files\Microsoft Visual Studio X\Common7\VS200XImageLibrary.

You don't state which version of Visual Studio you have installed but you'll need to replace the "200X" with your version number.

See this code. It will be help

public class ExtractIcon
{
    [DllImport("Shell32.dll")]
    private static extern int SHGetFileInfo(
        string pszPath, uint dwFileAttributes,
        out SHFILEINFO psfi, uint cbfileInfo,
        SHGFI uFlags);

    private struct SHFILEINFO
    {
        public SHFILEINFO(bool b)
        {
            hIcon = IntPtr.Zero; iIcon = 0; dwAttributes = 0; szDisplayName = ""; szTypeName = "";
        }
        public IntPtr hIcon;
        public int iIcon;
        public uint dwAttributes;
        public string szDisplayName;
        public string szTypeName;
    };

    private enum SHGFI
    {
        SmallIcon = 0x00000001,
        OpenIcon = 0x00000002,
        LargeIcon = 0x00000000,
        Icon = 0x00000100,
        DisplayName = 0x00000200,
        Typename = 0x00000400,
        SysIconIndex = 0x00004000,
        LinkOverlay = 0x00008000,
        UseFileAttributes = 0x00000010
    }

    public static Icon GetIcon(string strPath, bool bSmall, bool bOpen)
    {
        SHFILEINFO info = new SHFILEINFO(true);
        int cbFileInfo = Marshal.SizeOf(info);
        SHGFI flags;

        if (bSmall)
            flags = SHGFI.Icon | SHGFI.SmallIcon;
        else
            flags = SHGFI.Icon | SHGFI.LargeIcon;

        if (bOpen) flags = flags | SHGFI.OpenIcon;

        SHGetFileInfo(strPath, 0, out info, (uint)cbFileInfo, flags);

        return Icon.FromHandle(info.hIcon);
    }
}