You need to use the FillEffect.SetImage() method on the series. For example:
You can also see this in one of our sample. Open our Chart Explorer ( Start Menu -> All Programs -> Xceed Components -> Our components in action! -> Xceed Chart Explorer for .NET ), then go to All Examples -> Fill Effects -> Images You can look at the code by clicking on the "C# Code" tab. You will find the complete source code of the explorer in -> C:\Program Files\Xceed Components\Xceed Chart for .NET and ASP.NET \Samples under XP, or in C:\Xceed Component Samples\Xceed Chart for .NET \Samples under Vista.