Instead of using a d6 to show the escalation die, I created a spinner image that shows all 7 faces of the escalation die, starting with 0. I am including the image of the spinner itself along with some views of how mine is assembled.
Print the escalation image at whatever size you want. I did so on photo paper to make it look nicer. (I created this at a high resolution, oversized to allow you to retain quality and print at whatever size you need)
Create a stand for the spinner out of foam board. I used black foam board that you can find easily at Wal-Mart or any office supply store. Basically you are just creating a standing triangle (view the side photos for reference). If you score only one side of the foam board, it will allow you to fold it but remain together.
Adhere the spinner image to another, separate piece of foam board and cut around the outline for the heptagon (geometry is useful later in life!).
Punch a small hole in the center of the spinner and the stand. Place a screw with nut and washer through the hole, tightening it just enough to hold it, but loose enough to allow it to spin freely (with a bit of friction).
Paint or stick a small line, dot or arrow on the top of the stand (pictured in silver on mine).