I like to make fun of the whole theme idea...
Everyone tries to be original... So we did one year an "Original" theme. Everything in the Shalach Manos was labeled "original". Like "Original" Seltzer, original apple sauce etc...
Also did recession themed one a few years ago.
Did a recycled theme: We recycled purim baskets and containers from previous years and even tried to match it up if possible to some of the people who had given it to us in the past. We then put the most common Shalach Manos items; like grape juice, hamentashen, etc... with a nice little poem of how everyone recycles shalach manos and feel free to pass this one on as well.
Also did a morning after theme: 2 Tylenol, melba toast, powerade and rice cakes. All of these had nice little poems as I wouldn't expect most people to get it without explanations...