We are starting beta tests for WpfDiagram V2.3. The new features are:
 
Support for custom arrowheads
The type of the HeadShape, BaseShape and IntermediateShape properties of DiagramLink has been changed from enum ArrowHead to class Shape, which is also used to define ShapeNode shapes. The ArrowHeads class now exposes Shape definitions that correspond to the ArrowHead enumeration members from previous versions. It is also possible to assign any Shapes member or a custom shape as an arrowhead. When used for arrowheads, position (50, 0) in the shape definition corresponds to the arrowhead's tip point.

Adjustment handles styling
The ActiveItemHandlesColor, SelectedItemHandlesColor and DisabledHandlesColor properties have been replaced by ActiveItemHandlesStyle, SelectedItemHandlesStyle and DisabledHandlesStyle. The HandlesVisualStyle objects returned by them provide sub-properties for greater control over the appearance of selection handles. The adjustment handles can now be painted not only in solid color but with arbitrary brushes, such as LinearGradientBrush and ImageBrush objects.

Miscellaneous
~ The CancelDrag method allows cancelling the current draw operation when you need to start drag-and-drop with the Diagram as a source.
~ Granularity property added to QuickRouter.
~ The MinimumNodeSize property specifies the minimum size of nodes that can be set by the user interactively.
~ The DrawArrowhead method lets you render arrowhead shapes when custom-drawing.
 
If anyone is interested in trying the beta, please download this archive, which includes updated assemblies and help file:
https://mindfusion.eu/_beta/diagramming.wpf.2.3.zip