Making boutonnieres more special can be as simple as a ribbon wrap down the stem. You can also decide to accent with something like this River of Diamonds dazzle wrap.
It's commonly used for wrapping bridal bouquet stems and around cake. (This product is not approved for food, so you must put a protective layer between the Diamond wrap and the icing).
Because this is molded (it really doesn't contain rhinestones) it is an inexpensive element that can easily be cut into strips and bands with regular scissors.
Simply cut off the amount you need for your boutonniere or corsage.
You could wrap this around the stem as a sparkling band accent.