They are still just called Piebalds. If you can get them to have no markings at all, they are called 'High whites'.
Where are you located? Probably a million miles from me, but I am looking for some ASFs with smaller markings!
It's not a recessive trait. It's just that you can breed the ones with smaller and smaller markings together, and they will produce fewer and fewer spots. Ditto with the other direction, you can breed the piebald ones with big markings to other ones with big markings, and get bigger and bigger markings.
You can also make them have spots in specific places. If you find one with a spot you like, and breed it to one with a similar spot, you'll get more with the same kinds of spots!
Phew!