Just FYI, whenever we've tried to do this, we end up spending $, but here goes.
one idea is to ride the free boats. If you ride them back and forth, that eats quite a bit of time. If you'd done the MK area boats, consider something like the DTD resort shuttle boats.
In addition to spending time looking at decorations, you can spend a slow inexpensive lunch say, outside the GF QS, watching boats, watching the castle. Some vantage spots allow you to watch folks coming and going via bus at MK. It is interesting to see how many folks come and go.
You could perhaps get paid to take a DVC tour. Then, the tour is very much not free if you end up buying, but it is interesting to take the tour. the payback perks differ, but sometimes it is a gift card.(other times it is FP)
Besides holiday décor, you could go to any resort with a lake and walk around the lake. Likewise, if you haven't been to AoA, it is worth seeing all the regular décor at the resort. Many of the permanent displays are photo ops. (add in the animation class) The QS is also good place to get a inexpensive, healthy lunch perhaps.
The BWK area has the art gallery, and options for walking and exploring. At night you can kind of see Illuminations. Bonus to throw in the Swan/Dolphin.
People watch, almost any part of WDW.
tour the new Four Seasons resort, or really any area hotels. The Gaylord is also pretty neat.
I also second a hidden Mickey hunt. It does help to have the guide book or some other means of information on locating them (Online?)
Likewise, you could make your own scavenger hunt. You look at something like online images (or details) then try to locate those thing- like certain signs, or small details. I bet if you started a thread the DISers would love to help.
