Some people dress up for the holidays, but many others dress down—in the tackiest sweaters they can find. Since ugly sweaters took off in the 1980s, they have become more than just a holiday tradition. They’re a competitive sport: the more tinsel, lights, pom-poms and ornaments, the better! And these days you can really show them off. There are ugly sweater 5Ks, ugly sweater bar crawls, ugly sweater parties and of course, ugly sweater contests. Lisa Donofrio, a professor at the Fashion Institute of Technology in New York City who has designed Christmas sweaters, says you pretty much can’t go wrong whether you buy or DIY. “You can put on bows, bells or anything garish that sparks your fancy,” she notes. “It’s not about perfection, it’s about being over the…