I'm using your renderer, if you modify your code, the header's images are displayed ...
public override void DrawHeader( System.Drawing.Graphics graphics, System.Drawing.Rectangle bounds, string text, System.Drawing.Font font, System.Drawing.Image image, bool rtl )
{
....
if (image != null)
{
Rectangle r1 = new Rectangle(bounds.Right - image.Width - 4, (bounds.Top + (bounds.Height / 2)) - (image.Height / 2), image.Width, image.Height);
graphics.DrawImage(image, r1);
} }
/// Angel