pickles and onions is a midwest/plains thing. I have to request it at bbq joints in Bama that I have visited. No one bats an eye, except for one guy who looked at me like I dropped off a spaceship.
Also, Link and brisket sandwiches seem to be unknown down here. pity.
Alabama uses mayonnaise for barbecue sauce. Nuff said.
Pickles and onions are a standard side at a lot of the Q joints I go to here in Central Texas.