I've been stumped on this, as well, but got some fun ideas
here from others. My question focused on stalls, but I'm sure you could tweak them to be general decoration ideas:
Hot cocoa/cider/soup
Frozen treats
Hats/mittens/cooler weather pop-up shop
Pirate cove (I think that would be a fun beach/rock display, and could be spread out as much as you want
Maybe you could set up a series of chairs and fishing rods, with some fires, stools that have mugs and kettles on them, and do a winter fishing area (bonus is that if you break your rod, you can always go pluck another one

)