How old are your students? My little ones love doing anything with their handprints... you could have each kid trace their hand on colored construction paper, cut the hands out, and use them to "build" a holiday tree up one wall (you get to be the star on top, of course!).
If you can't use Christmas images, have each kid decorate a "present" for the wall, using a simple square of colored paper and whatever ribbons, spangles, stickers, etc you have on hand.
Older kids can make stained-"glass" windows... use a piece of clear cellophane as the base, add a black construction-paper border, and have them tape pieces of colored cellphone onto the clear piece to make their own designs. Much older kids can make mosaics this way, too.