Looking at "regular" items in a new way can reveal many options. Adding green and red bell peppers provide classic holiday colors to a wreath on the front door. An oddly-curled over-mature Armenian cucumber or long-necked gourd becomes a highlight in a table arrangement. A tree ornament becomes special when it's the only one on a wreath hung on a child's door, signifying his or her special place.
As simple as a bunch of favorite herb branches tied with a ribbon or as complex as a large and intricate wreath embellished with many sentimental items from a person's lifetime, materials can encompass anything you can get your hands on. Try grapevine trimmings off the back fence, pine cones fallen from the neighbor’s tree, posies you dried yourself or chili peppers you strung last summer, a whole sunflower head, eucalyptus foliage and pods, evergreen clippings -- pine, spruce, holly, redwood, cedar, osmanthus, juniper -- honeysuckle trimmings, magnolia leaves and seed cones, wisteria trimmings, fresh and dried fruits and nuts, dried Indian corn ears with husks partially removed to reveal colored kernels, dried rosebuds, and pyracantha berries and leaves.
Anything and everything becomes fair game when it comes to decorating. The essence of creativity is bringing materials together in a new and exciting way -- it's all up to you and your innate cleverness and sense of humor.