I'll be honest the Tesla is the worst interior to me with it's giant iPad in the dash. I hate that. That says a lot considering the Aztek is on the list. To me the Tesla interior has quality control issues a 1980's Toyota would be unfamiliar with.
Boy interiors were so elegant and appointed in the earliest days on the finest cars. You could argue that in some ways today's best isn't quite that level.
"How many other brands stuck with an interior conceit for that long?"
(I'll assume you meant "concept"... darned spell-check robot)
I submit to you the Chrysler Highlander interior (which debuted in 1940).
and the 1976 Chrysler Newport w/Highlander interior...
I also recall seeing some promo photos of a 1982 Lebaron Convertible with plaid interior, but I don't know if that made production and Google can't find it either.