l am trying load images with ajax into a div.

l am trying load images with ajax into a div.

l am trying load images with ajax into a div with c#  web method code behind. 

My div: 
  1.          <div id="ThumbNailNav" style="display: block; width:100%; height:100px; z-index:1; background-       color:Red" title="Thumbnail Navigation" >
             <div id="thumbimg" style="width:80px; height:80px">
            </div>
         </div>

My ajax code:
  1.   function PopulateThumbsEx(BookID, lastShown) {
  2.             var tag = $("<div></div>");
  3.             $.ajax({
  4.                 type: "POST", // AJAX type post
  5.                 url: "tabletbook.aspx/GetThumbNailPage",
  6.                 data: '{"BookID": "' + BookID + '",  "lastShown": "' + lastShown + '"}',
  7.                 contentType: "application/json; charset=utf-8", //This is required or you will get all sorts of strange things :-)
  8.                 dataType: "json", //We need to specifiy JSON as to have the AJAX serilize the data between Client and server 
  9.                 success: function (data) { // The msg that comes back has in it the d attribute which in this case contains an array from the server
  10.                     thumbnails = data.d; //Lets copy the links to a global array this gets set by the odd guy. andthen the even comes in right after and sets it
  11.                     // so when the odd goes to render the global has the even values in it. hard to debug because you are introducing pauesse that won't exist normally ok.
  12.                     //tag.html(data).dialog({ modal: true }).mobile.changePage('#ThumbNailNavDialog');
  13.                     $("#thumbimg").empty();
  14.                     $("#thumbimg").css("z-index", "3");
  15.                     $("#thumbimg").append(thumbnails);
  16.                     $("#thumbimg").fadeIn("fast");
  17.                 }
  18.             });
  19.         }
My web method 

  1.     [WebMethod(true)]
  2.         public static string GetThumbNailPage(int BookID, int lastShown)
  3.         {
  4.             BookDC bdc = new BookDC();
  5.             FlipBook book = bdc.GetBook(BookID);
  6.             string s = book.ClientID.ToString();

  7.             //Lets get a list to the thumbnail files
  8.             List<string> tnFiles = Common.helpers.ExtractImagesFromFolder(HttpContext.Current.Server.MapPath("~/Clients/" + s + "/" + BookID.ToString() + "/Thumbs"));
  9.             StringBuilder sb = new StringBuilder();
  10.             string[] fileList = tnFiles.ToArray();
  11.             Array.Sort(fileList, new Common.NaturalComparer());
  12.             tnFiles.Clear();
  13.             tnFiles.AddRange(fileList);
  14.             sb.AppendLine("<table  style='margin-left:auto;margin-right:auto' cellpadding='5' width='100%' rel='{*}' id='tblThumbs' >");
  15.             if (lastShown == tnFiles.Count)
  16.             {
  17.                 lastShown = 0;
  18.             }
  19.             if (lastShown < 0)
  20.             {
  21.                 lastShown = 0;
  22.             }
  23.             string PgNum = "";
  24.             for (int r = 0; r < 4; r++)
  25.             {
  26.                 sb.AppendLine("<tr>");
  27.                 for (int c = 0; c < 5; c++)
  28.                 {
  29.                     if (lastShown < tnFiles.Count)
  30.                     {
  31.                         FileInfo FI = new FileInfo(tnFiles[lastShown]);
  32.                         string FileName = FI.Name; // get the
  33.                         lastShown++;

  34.                         PgNum = FileName.Substring(FileName.IndexOf("-") + 1);
  35.                         PgNum = PgNum.Substring(0, PgNum.IndexOf("."));

  36.                         sb.AppendLine("<td><a href='#'><img  class='thumbNailLink' title='" + PgNum + "' src='"
  37.                             + "/Clients/" + s + "/" + BookID.ToString() + "/Thumbs/" + FileName + "' ></a></td>");
  38.                     }
  39.                 }
  40.                 sb.AppendLine("</tr>");
  41.             }
  42.             sb.AppendLine("</table>");
  43.             string retStr = sb.ToString().Replace("{*}", lastShown.ToString());
  44.             return retStr;
  45.         }
The images are not showing how do I fix this.