I don't own the DVD, but I did a search for easter eggs (hidden features) on it. Sorry, no never before seen footage, but I did find a couple of cool things:
On the main title page and in the bonus material menu, click on the white snowflake in the lower left hand corner of your screen, and it will start snowing in the snowglobe
The special edition DVD contains a mini game in which you act as Santa and deliver presents all while avoiding troublesome ducks and tall buildings. If you complete this game successfully, you get a small reward
in the form of the 'Silly Symphonies' cartoon 'The Night Before Christmas.'