Your bouquet is an important detail to personalize and make your own. The bouquet should compliment the other details you have already selected, especially your dress. Think of it as another accessory.
As with everything wedding planning, there are tons of options out there for what to go with. Along with color and embellishments, there are different shapes available for your bouquet. The most popular and traditional bouquets are nosegay or round cluster bouquets; they are classic, tightly-packed round bouquets that are full of flowers. For very formal affairs, cascade bouquets may be a good match. Cascade bouquets fall down, either just slightly or more dramatically. Although becoming more and more popular, hand-tied bouquets are usually used for less formal affairs. But, depending on the flowers and ribbon selections, they can be seen as more formal too.
A few more shapes of bouquets are listed at brides.com.