Ooh! I can help with this one!
For our trip this past year, I bought Mickey and Friends stickers and placed them nicely on the cover. Inside the first flap I actually created a spreadsheet of our day to day plans. On the next flap I printed out all our ADR's along with their confirmation numbers, locations, and dates.
On the back flaps I printed out alllll the phone numbers we need. I realize that these can be found within the passporter, but I made sure I had the 800 number for Disney, ASMO's phone number, and other contact information.