I didn't get a chance to read everything so far, but my main comment is to enjoy!!
Enjoy touring on your own schedule. Get up when you want, leave when you want.
I did see the photo ideas mentioned. A great place to get sign pictures is in Animal Kingdom. They're everywhere, and many are quite clever.
Look for Hidden Mickey's.
Just walk aimlessly around World Showcase. Especially at night before Illuminations...then just stop right before the torches are "blown" out.
Again, especially in World Showcase, talk to the cast members. Most of the college program kids (in all parks) are enthusiastic and happy to chat.
If you have a car and a rainy day, go to the outlets for awhile.
Take advantage of some of the single rider lines. Test Track is a great one.
Eat where you want and when you want.
And most of all, have fun!