The Lampropeltis genus has always been my favorite of the North American colubrids. During the period of the Great Contraction, when I decided to bring my collection under control I sold many of the projects I was working with and unfortunately do not have pictures of them.
Some of the kings, including the often recommended California king, can be nippy, particularly as hatchlings, and some are prone to the occasional exploratory bite when being held. Others however, are very docile. As always, it depends much on the individual, and there are always exceptions, but from my experience most of the various species can be catagorized with a certain extent of accuracy. All the mountain king species I have kept and the nelson's milks have proven to be exceptionally docile in my collection. Likewise, I never had any trouble out of the mexican black king group I had, but most of my hatchling cal kings are quick to defend themselves, and the adults are generally very quick with the feeding strike, even if you don't have a mouse in hand.
The adult brooksi I have kept were known for their tendency to give you a test bite if there was a scent of anything at all on you. If they pressed their nose into your arm, you were about to be chewed on.
They also proved the most problematic to breed, as they were equally likely to fight and attempt to consume each other as they were to copulate when introduced.
All in all though these are an exceptional group of snakes to keep, and there's pretty much something for everybody among the varied species, and the care of adults is basically the same for all species.
Lowland varieties are the easiest to produce. The mountain kings of the pyromelana and zonata species as well as the gray banded kings to a certain extent can be difficult to get started on pinks after hatching, sometimes extremely difficult, but are a nice challenge for the seasoned breeder of the easier species.