Topiaries are pretty any time of the year, but I love them now especially. My local Home Depot had a fresh shipment of rosemary yesterday in a variety of shapes and sizes at great prices!
Fresh citrus is also pretty any time, but I do associate it (especially oranges) with the holidays. A bowl full of lemons, limes, or oranges adds a nice pop of color and you always have a healthy snack or slice to flavor your water on hand.
Fresh branches of just about anything add a nice touch too. Magnolia happens to be one of my favorites.
I like to add a subtle fragrance when the seasons change. This combination of cinnamon, nutmeg, cloves, rosemary, and pine needles sounds perfect for the season.
Pine cones are another favorite. Here is a great tutorial for making a garland out of large pine cones.
Images: 1, 2, 3, 4, 5