Last time we did the HD Mickey heads. We numbered them and put a trivia question or fun fact under each one. Under the question was a picture of the WDW attraction or character that gave them the answer. My girls took turns pulling off the Mickey head and reading the question every day.
This year I did the following for our upcoming trip. I gave it to my girls as a Xmas gift. Every time we go to Disney and every Xmas, I always buy a bunch of Disney pins on eBay so my daughters can use them for trading. This year I tried to incorporate the pins into the countdown calendar. The way it works, is that the girls will take turns removing a pin each day right up to our departure day. They can keep the pin if they like or add it their trading lanyard.
For the calendar itself, it is pretty simple. I used Powerpoint with the fireworks background template, the Waltograph font that you can find for free online, and various clip art that I also downloaded for free in various spots. Then I just poked the pins thru the back and attached the Mickey backing on the front. On the back I covered each pin with a Mickey head cut out so that you can't see any of the pins for the upcoming days when you are removing the current day's pin (the HD heads were too big for this)
Here is the powerpoint file. You can customized it with your own colors and clip art:
countdown1.ppt
And here is where I downloaded the font:
http://www.dafont.com/walt-disney.font