sending images with out attachements in mail

My requirement is to send images in mail with out attachements ,i tried like this it works for single attachement and  if i attach second image is not displaying,my code is
 
public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Write(sentmail("tubetv9@gmail.com", "tubetv9@gmail.com", "hi"));
    }
    public string sentmail(string to, string from, string subject)
    {
        MailMessage message = new MailMessage();
        SmtpClient smtpc = new ...