To add to what Dr. Del posted, even plain black pastels have a different head shape than a normal ball pythons -- they have a sharper look to them. Pastels seems a little different to me, but I can't say for sure that it isn't something about the color scheme.

Another thing to kinda keep in mind, is their head shapes change a lot with maturity. This is just a personal observation, but lot of the animals we breed are really breedable subadults. Just from my own critters, it seems like head shape changes around age 4 or 5 and is most noticeable in females. And especially in females who have successfully bred. In other species, carpets for instance, it's way more pronounced.