|This is not a thing we're doing for at least three distinct reasons.|
As I said in my wedding FAQ's, I've been asked this question more than once:
Q: You're getting married? Congratulations! What's your theme?
A: Oh, you know, marriage.
More detailed A: Our wedding will be straight from the Book of Common Prayer, hopefully with a little music by friends, and there will be snacks. By the end of it, we'll be married.
People* who haven't recently spent time flipping through wedding magazines and blogs** might be unaware, but all the cool weddings these days have themes. Not explorations of timeless ideas and universal questions, like in literature; more like pervasive motifs, like in amusement parks and children's birthday parties.
Some people manage to have a theme in an un-obnoxious way. Here are an Amelie wedding and an Up wedding that pull it off sweetly. My brother and sister-in-law also rocked an Alice in Wonderland theme for their reception (after a BCP ceremony). Those are fun to go to, but they don't suit Blade and me. Also, these weddings are unusually labor-intensive, and, as Lisa puts it, I react to wedding chores the way Harry Potter characters react to Dementors.
And let's not forget that wedding themes often veer into crazy: How about a Star Wars wedding? Or a pirate theatrical classic rock wedding? (Both of these weddings were recently posted on Offbeat Bride, where a staggering number of weddings feature a TARDIS.)
People obviously put loads of care into themed weddings, but, at least from the pictures, many of these events seem less about sacrament and more about entertainment.
I wonder if this trend toward themes is a reaction against being told What Is Expected for a Proper Wedding over and over by (mostly) well-meaning friends and family from the moment you get engaged. I respond to that pressure by delegating to someone more useful than I am, just before I curl into a fetal position. I'm lucky that the people whose opinions matter most to me also like laid back, simple things.
*This is most people, right? I hope and pray that it is most people.
**Most of which are designed to make you insane.