Sometimes the solution is: simplify. If your centerpieces are modern concoctions of orchids and succulents, pair the elements down to their essentials and use them in the cocktail table arrangements, as shown below.
Other times the solution is: go wacky. The cocktail hour is usually when guests relax before the "big event" of a formal dinner, so a whimsical floral can be just the thing, like the gerbers or birdcages below, both of which played off the overall theme decor (one a mitzvah, one a nightclub party).
Another solution: go bold. Choose one color from the centerpieces and use it alone in the cocktail table arrangements. This works especially well if the other decor is minimalist or neutral colors.
