You can add images to events using BeforeEventRender event handler:
protected void DayPilotMonth1_BeforeEventRender(object sender, DayPilot.Web.Ui.Events.Month.BeforeEventRenderEventArgs e) { if (e.Value == "11") { e.InnerHTML = String.Format("<img src='../Media/red8x8.gif' width='8' height='8' valign='absmiddle' /> {0}", e.InnerHTML); } }
See also Demo/Month/CustomEventRendering.aspx.cs in the DayPilot package.