cuetools.net/taglib-sharp/examples/SetPictures.cs

using System;
using TagLib;

public class SetPictures
{
    public static void Main(string [] args)
    {
        if(args.Length < 2) {
            Console.Error.WriteLine("USAGE: mono SetPictures.exe AUDIO_PATH IMAGE_PATH_1[...IMAGE_PATH_N]");
            return;
        }
    
        TagLib.File file = TagLib.File.Create(args[0]);
        Console.WriteLine("Current picture count: " + file.Tag.Pictures.Length);
        
        Picture [] pictures = new Picture[args.Length - 1];
    
        for(int i = 1; i < args.Length; i++) {
            Picture picture = new Picture(args[i]);
            pictures[i - 1] = picture;
        }
        
        file.Tag.Pictures = pictures;
        file.Save();
        
        Console.WriteLine("New picture count: " + file.Tag.Pictures.Length);
    }
}