One wedding I officiated years ago was a "circus" wedding... with real circus acts and clowns. I was dressed in a ring-master's outfit and the guests got to eat cotton candy and peanuts during the ceremony. A real blast!
Halloween weddings can be lots of fun. I've officiated many of these over the years, both in costume and out. I even had a halloween party at my office one year and a couple talked me in to doing their ceremony at my own party!
Costume weddings can be fun, even if it's not Halloween.
Roller-Coasters! Of course, anyone who looks at my website can see I've married couples on top of a roller-coaster. Of course, you might have trouble getting permission for this type of wedding... but it might be worth a try.
Do you like animals? Well, a Zoo wedding might be something to consider. The Los Angeles Zoo has a special wedding package, and they can even cater the affair on the zoo grounds.
Fifties weddings can be lots of fun. From poodle skirts to duck-tails, even if you aren't from that era, you can have a great time.
Hawaiian style weddings are lots of fun... I've done many of these over the year. Hawaiian shirts and sarongs are the rage for this type of wedding.
Skydiving? Ok, I haven't done one of these yet... but I might consider it.
Weddings on horseback can be a great way to tie the knot. However, if you are not a horseman or woman... have a soft pillow ready for your you know what.
These are just a few examples to consider... but let your imagination run wild! When it comes to theme weddings, having a good time is the key!