I think the major difference between dog breeding and snake breeding is that dogs are bred to get that special shape head, body and tail and for the character qualities a particular breed of dogs has. Color is often secondairy. A perfect labrador can be black, chocolat brown, blond but can by shape and character still be a perfect labrador. For snakes we mostly check for colour and patern. There is no breeder worrying about character even though some claim that some combo’s have a different behaviour. Like a discussion there was on the forum on the “adventurous nature” of mojaves or the stories on the more defensive super cinny’s, super black pastels and 8balls.
The same with headshape, it’s not an issue in breeding as long as it is healthy ( no duckbilling, small eyes, bug eyes). I indeed see different healthy head shapes. My banana male has a very long triangular, flat head. Everytime I take him out I really notice it. My pastel female I bought last has a real beefy head, short and stout. My albino girl has a slim pointy nose, and my albino pied male has that hourglas shape, like he has big brains and a slim nose, my cinny fire girl has really big eyes, but it fits her head ect ect. But for as long as there are no real irregularitys there is no standard shape to breed for. Just like there is no size to breed for. I at least never heard any breeder mention that he is trying to breed for the bigger sized, or smaller ball python. They are in every size perfect for any snake keeper. It’s only about breeding healthy most beautiful snakes.
In boa’s and retics breeding size is something they do breed for or at least claim to breed for. But that is mainly because in the “avarage” size they can be too big for a lot of people, so there is breeding for dwarf and super dwarf retics and breeding different boa localities because of the difference in size. But I also never heard anyone making breeding plans based on headshapes for those two. The major thing is simply getting those stunning patterns and colours.