We could do this with tennis balls.
Tennis party by Tracey Pred
Google Image Result for http://www.sportspartyworld.com/items/ten_items/cupcake4.jpg
Tennis Themed party
tennis centerpieces for parties - Google Search
tennis centerpiece mitzvah by The Prop Factory, via Flickr
Tennis ball napkin rings. Hmm best to use a new can of balls for formal occasions.
Hm. You don't see them from this angle very often...Tennis ball wreath!