Serving punch? Depending on the shape of your bowl, you can easily dress up the base with a ring of carnations, stems removed. Now, don't wrinkle your nose. Carnations have a pleasant scent, come in pretty colors, and look lovely when grouped together. In short, they're great for decorating.
This works best with a punch bowl that doesn't have a foot. You could use any flower that has a good amount of texture (so, no tulips). Stargazer lilies might be interesting. I did the arrangement below at the last minute when setting up for a friend's birthday party by the lake, and it turned out so cute! Chose flowers that coordinate with the punch and tablecloth, as shown here.