Please refer this link

Display Images from Folder in ASP.Net

If you want to use DataTable instead of List please refer this code.

C#

protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      DataTable dt = new DataTable();
      dt.Columns.AddRange(new DataColumn[2] { new DataColumn("Name"), new DataColumn("Url") });
      string[] files = System.IO.Directory.GetFiles(Server.MapPath("~/images/"), "*");
      foreach (string file in files)
      {
          dt.Rows.Add(System.IO.Path.GetFileName(file), "~/images/" + System.IO.Path.GetFileName(file));
      }
      GridView1.DataSource = dt;
      GridView1.DataBind();
    }
}