I actually think the strings of lights are so festive! I've been at the BWV over Christmas a couple times, and it's so cute. We had a little tree with lights on the armoire in the living room, and hung up our stockings with 3M hooks (which fell off the wall a few times - not super good hooks). I put festive clings on the door to the balcony. Tried doing outside lights, but extension cord was too short. But lots of folks had them (and I saw folks checking in, obviously had driven, with boxes containing larger Christmas trees).
At Pop, many folks decorate their windows and doors. It's cute. Long as you don't use tape or anything like that, clings and suction cups are fine!
I also wasn't ever told not to do any decorations that were visible from the outside. I've heard this mentioned, but in all my stays at
DVC resorts, only thing I have heard for certain is at AKL/AKV for animals' protection no balloons or things like that.