Any topiary that has foam underneath its greenery can get this unusual and inexpensive holiday treatment: garlic cloves. Pull apart a head of garlic and separate the largest cloves. Use heavy-gauge florist's wire to spear each clove, then push the other end of the wire into the topiary's foam.
You can continue the garlic theme by wiring more cloves to a wreath or into a greenery swag on the mantel. For the first couple of days, the room will smell like garlic -- but no more strongly than if you were cooking with the fresh cloves. After that the scent will fade. If you find the scent too strong, consider leaving the topiaries outdoors for a couple of days.