This does sound like fun.
If I were doing this, I'd make my sweater look like the skirt of a Christmas tree (glue on pine needles, bits of tinsel, glitter, and maybe even a stray Christmas ornament or two). Then I'd glue on crumpled wrapping paper, ripped bits of wrapping paper, pieces of gift bags (or maybe even a whole small one), name tags, and a small empty box or two.
In other words, I'd look like the gosh-awful mess around the tree right after all the Christmas presents have been opened! That's the messiest (i.e., tackiest) time of the year--but also the happiest, too!
Please post a picture. We'd love to see your creation!