<asp:DataGrid id="DataGrid1" 
    OnItemDataBound="DataGrid1_ItemDataBound" ....>
....
</asp:DataGrid>

protected void DataGrid1_ItemDataBound(
    object sender, DataGridItemEventArgs e)
{
    if ((e.Item.ItemType == ListItemType.Item) ||
        (e.Item.ItemType == ListItemType.AlternatingItem))
    {
        //Find the ImageZoom control for this row
        EO.Web.ImageZoom iz = (EO.Web.ImageZoom)e.Item.FindControl("ImageZoom1");

        //The following code creates a dynamic ClientTemplate 
        //for this ImageZoom control. 
        ClientTemplate template = new ClientTemplate();

        //Get your data. For example, if you have "TakenBy"
        //in your DB, you can get it from here. Note the type
        //of e.Item.DataItem depends on the type of your
        //data source. So you may need to change DataRowRow
        //to something else.
        DataRowView row = (DataRowView)e.Item.DataItem;

        //This code just get the big image Url because it's
        //what's available in our sample data source. You will
        //need to change this
        string imageUrl = (string)row["BigImage"];

        //Now creates the dynamic template text based on
        //whatever logic you have. 
        template.Text = string.Format("<p>{{var:big_image}}</p><p>Url: {0}</p>", imageUrl);

        //Assign the template to the ImageZoom control
        iz.ZoomPanelTemplate = template;
    }
}