Hi Changmin,
Yes you can assign an image to a marker using the NImageFillStyle - for example:
NPointSeries point = new NPointSeries();
point.Size = new NLength(0);
point.DataLabelStyle.Visible = false;
point.MarkerStyle.Visible = true;
point.MarkerStyle.FillStyle = new NImageFillStyle("c:\\temp\\markerimage.png");
point.Values.Add(10);
chart.Series.Add(point);
We hope this helps - let us know if you have any questions.
Best Regards,
Nevron Support Team