The Dispose method, which is inherited from UIElement, automatically disposes all children which are returned from derived classes as virtual children. But additional objects like the Setter's Value or additional DataTemplates, which all also potentially contain disposable objects, aren't disposed currently.

h4. Additional Information
What is to do?
Check all classes in SkinEngine.Controls and SpecialControls for properties which are not part of the visual tree and which are not correctly disposed. Call UIElement.TryCleanupAndDispose for them in the Dispose method.