Stripe and Motley are genetic. In fact, they're on the same allele. It's even been postulated that Motley is dominant with regards to Stripe.
That having been said, the degree of dorsal motley patterning definitely varies with lines (Hurricane motleys being a prime example). It's also possible to line-breed normal corns to eventually produce a motley dorsal pattern without the motley gene component.
Banded... is line bred so far as I've heard. You can have motleys line-bred to have a banded appearance, and you can have non-motleys line-bred to have a banded appearance. There is (atleast at this time) no 'banded' gene.
I'm unaware of what morphs exist in other species of snake, so I can't answer that part of the question... That having been said, cornsnakes seem to be a wellspring of pattern and color mutations, some of which have not been seen in other species yet. Yet. It's always possible that five years down the road someone will produce a motley obsoleta or something.
-Kat
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"You keep WHAT in your freezer?"
"Mice. And rats. If that bothers you, I can call them 'cows' instead."