Boxwood is a lovely greenery that is a favorite of mine for all arrangements - including holiday ones. It has a little bittersweet smell - but you don't really notice it mixed in with the wonderful pine and spruce aroma.
Tuck some sprigs in here and there to add more shades of green and an interesting texture.
Cluster some in close to the center, right next to the hurricane glass.
Sometimes a little variegation can add a nice contrast as well. This one is call pittosporum. It is available all year round.
Tuck some in here and there for nice contrast. Please note that most pittosporum leaves are edged in an off white.
When my greening is complete, I use a leaf polish like Leafshine to give it a nice glossy finishing and seal the greenery. I don't consider it as essential as I do Finishing Touch, but it is a product that I favor and like to use.
Spray it on only greenery - it is not meant to seal fresh flowers. For that, you'll need to use Finishing Touch (which is fine to use on both flowers and greenery - but it will NOT leave the glossy sheen that Leaf Shine does on greens).
Keep in mind that what sets a professional florist apart from an amateur is the way they process their flowers and treat their final designs. Using floral products like this doesn't add that much to a the final expense of a large event and really does change the look of your flowers and extends the life of the arrangements.