Do you have a theme or a requirement on your stall? (In our school, each class gets told their overall requirement - sweet stall, bottle draw, cake stall, toys stall, books stall, etc).
Following on from Reindeers of sweets, how about bags of "Snowman Soup"? Cellophane bags with a serving of hot chocolate powder (either individual sachets for ease, or measured out into small bags and tied off from a tub), a candy cane to stir, and a couple of mini marshmallows. There are lots and lots of different versions of the "poem" out there on the web, many of which can be printed to either put in the bag or used as a "topper" on the top of the bag, to explain it.
"Reindeer Poop" is another (chocolate covered raisins) that can be doled out into cello bags and a poem added.
"Snowman poop" could be white bon-bons - or the blue ones if you find those.
I see lots of different chocolate cupcakes made into Reindeers with mini-pretzels for antlers, and something like a red smartie as a nose as part of the icing decorations.
Do you just want to sell things, or could people make things there?
A great one in our school is the Santa's workshop - there is a Santa's Grotto to meet the man, but there's another where the parents in charge supervise Elves (6th class kids) bringing kids from the other classes to another room, where they can choose small presents for their DPs, and get them wrapped (themselves or the Elves do it), in secret, so they just bring out a paper bag with the wrapped items in it. Most DPs know what they are getting before they leave school - but the DCs get to choose in secret if they want. This is the one stall that requires money to be given in advance (you say whether you want 1 or 2 presents) to ensure that there are enough items. Costs €3 per present and the actual presents are small items (tree decorations, sort of adult stocking filler things, lots of small tools or nice mini-toiletries or things from Tiger etc, some are funny, some are useful, some are just tat, but the DCs get to choose themselves!)
Those are my main seasonal ideas anyway.