The one plant that universally says "Christmas" is undoubtedly the poinsettia or Euphorbia pulcherrima. It's native to rainforests in Mexico and Central America and does pretty well as a houseplant for a month or two.
Right now I'm on the look-out for some to decorate our home and office. With proper care they should look great throughout the Christmas season and well into the New Year.
Place your poinsettia in a sunny room. Their ideal temperature hovers between 60 and 70 degrees.
One thing to avoid is drafts! A few years ago, I purchased large (pricey) plants for the patio and front porch. What a mistake! The wind beat the tar out of them and I spend the holidays sweeping up dropped leaves. Years ago I used to purchase large poinsettia hanging baskets at The Flower Pot in Harlingen. They hung on our screened porch and just invited you outside- but that porch had great protection from the breeze. Lesson learned.
A second thing you want to avoid is placing them near a heat source. I may love a roaring fire on a cold winter night but they do not.
Poinsettias come in many colors to match any home and Christmas decor. I adore the white ones - but this year, we're going colorful so red it is!