At maturity trees can have a wide range of canopy forms, created naturally as opposed to created by training/pruning.
Canopies can range from upright, almost columnar (fastigiate), flame shaped, oval (upright), rounded, domed, bell shaped and irregular. They can occur from the ground or well clear stem themselves as they mature.
With regard to the variety of clipped/trained canopies, this is making my head spin at present. Will attempt to outline these later.