Are you familiar with GDI? You need to know something about GDI in order to make use of this feature.
When you set the OwnerDraw to true, whenever the menu has to be painted, it will trigger the DrawItem event. The event passes you a a DrawItemEventArgs which contains a Graphics object and Bounds. The Bounds is the dimensions of the area for you to draw. You can use the methods of Graphics to write or draw anything you like and also add images.
The MSDN Library documentation for DrawItem event has an example. If it is not illuminating enough, try a search on DrawItem. There are many examples out there. But you would still need to know GDI.