// .aspx
<asp:Repeater ID="BannerRepeater" runat="server">
    <ItemTemplate>
        <asp:Image
            ID="Image1"
            ImageUrl='<%# "res/img/banner/" + Eval("Name") %>'
            runat="server"
            AlternateText="bannerimg"
            CssClass="bannerImg" />
    </ItemTemplate>
</asp:Repeater>

    // .cs
        string root;
        List<FileInfo> files;

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                files = new List<FileInfo>();
                root = System.Web.HttpContext.Current.Request.ServerVariables["APPL_PHYSICAL_PATH"];

                foreach (string file in Directory.GetFiles(root + @"res\img\banner", "*.jpg"))
                    files.Add(new FileInfo(file));

                BannerRepeater.DataSource = files;
                BannerRepeater.DataBind();
            }
        }