Crawl Sequential URLs

Add a rule to Fiddler with Global scope as follows:

    public static ToolsAction("Crawl Sequential URLs") 
    function doCrawl(){ 
      var sBase: String;
      var sInt: String;

      sBase = FiddlerObject.prompt("Enter base URL with ## in place of the start integer", "http://www.example.com/img##.jpg");
      sInt = FiddlerObject.prompt("Start At", "1");
      var iFirst = int.Parse(sInt);
      sInt = FiddlerObject.prompt("End At", "12");
      var iLast = int.Parse(sInt);

      for (var x=iFirst; x<=iLast; x++)
      {
        //Replace 's' with your HTTP Request. Note: \ is a special character in JScript
        // If you want to represent a backslash in a string constant, double it like \\ 
        var s = "GET " + sBase.Replace("##", x.ToString()) + " HTTP/1.0\r\n\r\n"; 
        var b=false;
        while(!b){
        try{
          FiddlerObject.utilIssueRequest(s);
          b=true;
        }
        catch(e){
          var iT = Environment.TickCount + 10000;
          FiddlerObject.StatusText = "Waiting 10 sec because we have too many requests outstanding...";
          while (iT > Environment.TickCount){ Application.DoEvents(); }
          } 
        }
      }
    }