Download the Plugin from here http://jquery.eisbehr.de/lazy/index.php
HTML
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script src="jquery.lazy.1.6.min.js" type="text/javascript"></script>
<script type = "text/javascript">
$(function () {
$("[id*=GridView1] img").lazy();
});
</script>
<asp:GridView ID = "GridView1" runat="server" AutoGenerateColumns = "false">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:Image runat = "server" data-src = '<%# Eval("ImageUrl") %>' src = "loading.gif" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Code
protected void Page_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[1] {
new DataColumn("ImageUrl", typeof(string))});
dt.Rows.Add("JellyFish.jpg");
dt.Rows.Add("Koala.jpg");
dt.Rows.Add("Penguins.jpg");
dt.Rows.Add("Tulips.jpg");
GridView1.DataSource = dt;
GridView1.DataBind();
}