short answer: something fabulous! (obviously.) when you look great, you feel great, right? and we want everyone to be feeling great and having fun on our wedding day.
slightly longer answer: though we do hope everyone wants to make themselves all spiffy for the festivities, we're slightly more concerned with what not to wear (also one of eliza's favorite tv shows) - black.
i know, i know, you have this awesome little black dress/black suit you want to wear, don't you? well, it used to be against all wedding guest rules to wear black because it was seen as a statement against the marriage. while we know that's not really the case anymore, there are so many people making statements against our marriage around the world that having black attire at our wedding just doesn't feel right to us. it's kind of our own personal version of the white knots. we hope you understand.