Back in college, I worked three jobs. One was at my brother-in-law's hot dog stand, where hot dogs were made "Chicago-style." There was no ketchup. Mustard went on first, then tomato wedges and diced onions and cucumbers which we had sliced and partially peeled to give the appearance of stripes on the sides. If desired, hot or sweet peppers topped that and then celery salt was sprinkled on top. I still love to throw a little celery salt on top.
My son had some buddies over recently and we had made burgers, bratwurst and hot dogs. He topped his with ketchup, mustard and grilled onions and mushrooms. Interesting. What do you put on yours?