My Peavey 6534+ came in a big cardboard box (the Peavey box) with egg carton type corners inside it to space it away from the side of the box and wrapped in bubble wrap (inside the box) if I remember correctly. I'm pretty sure it was inside some kind of waterproof courier bag too
Sorry but this is the only photo I have of the box.

It was absolutely fine. I will say though that Peaveys are famously durable though. Some amps probably don't take as much punishment. As you can see there are no dents in the box, so maybe I was just lucky