Ti ho già fatto avere un esempio funzionante. Ne vuoi un altro, senza usare database? che produca una tabella? Eccolo:
codice:
<%@ Page Language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
        Dim p_img As String = RequestParams("p_img")
        Dim p_max As String = RequestParams("p_max")
        
        If p_img <> "" AndAlso p_max <> "" Then
            ReturnImg(p_img, p_max)
        End If
        
        Dim a() As String = IO.Directory.GetFiles("C:\dati\Prove Nicon", "*.jpg", IO.SearchOption.TopDirectoryOnly)
        Dim b(a.GetUpperBound(0)) As String
        For i As Integer = 0 To a.Length - 1
            b(i) = String.Format("[img][/img]", i, Path.GetFileName(a(i)))
        Next
        Me.DataList1.DataSource = b
        Me.DataList1.DataBind()
    End Sub
    
    Private Sub ReturnImg(ByVal p_img As String, ByVal p_max As String)
        Dim p_clip As String = RequestParams("p_clip")
        If p_clip = "1" Then
            Dim border As Integer = 4
            Dim bmp As Bitmap = img.ImgLoad(p_img)
            img.ImgClipSquare(bmp, CInt(p_max) - border - border)
            img.ImgBorder(bmp, border, Color.White)
            img.ImgSaveToResponseOutputStream(bmp)
        Else
            img.ImgResizeAndSaveToResponseOutputStream(p_img, CInt(p_max))
        End If
        
    End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Pagina senza titolo</title>
	<link rel="stylesheet" href="css/lightbox.css" type="text/css" media="screen" />
	
	<script src="js/prototype.js" type="text/javascript"></script>
	<script src="js/scriptaculous.js?load=effects" type="text/javascript"></script>
	<script src="js/lightbox.js" type="text/javascript"></script>

	<style type="text/css">
		body{ color: #333; font: 13px 'Lucida Grande', Verdana, sans-serif;	}
        H3	
        {	
	        COLOR: #003366;
	        font-family: Verdana, Arial, Helvetica, sans-serif;
	        font-size:	1.58em;
	        font-weight:	500;
	        font-style:	normal;
	        text-decoration:	none;
	        word-spacing:	normal;
	        letter-spacing:	normal;
	        text-transform:	none;
	    }	
		
	</style>
    <script type="text/javascript" src="../../js/libreria_no_ajax.comp.js"></script>
</head>
<body>
    <div id="div_readonly" style="position:absolute; z-index:99999; left:100px;top:100px; width:250px; height:50px; background-color:White; border:1px black solid; padding:10px; text-align:center; display:" >
        Prego attendere: operazione in corso...

        [img]../../immagini/pleasewait.gif[/img]
    </div>
    <h3>Prova lettura immagini da cartella e ingrandimento con lightbox</h3>
    <form id="form1" runat="server">
	    <asp:datalist id="DataList1" runat="server" RepeatColumns="4" CellPadding="3" BorderWidth="1px" GridLines="Both" EnableViewState="false">
		    <ItemTemplate>
			    <%#Container.DataItem()%>
		    </ItemTemplate>
	    </asp:datalist>
    </form>
    <script type="text/javascript">
        disabilita_pagina(50);addLoadEvent(function(){abilita_pagina();
        $("div_readonly").style.display="none";});
    </script>
    
</body>
</html>