Destroy first calls UnRegisterChanges to unregister any objects registered to receive notification when the image list changed, and frees all helper objects associated with the image list. 

Destroy seldom needs to be called. However, when an image list is constructed without an owner by the Create or CreateSize method, call Free to release memory and dispose of the object. Free checks to see if the pointer is nil before calling Destroy. 

System::TObject::Free 

UnRegisterChanges