Help!

You can have an umbrella as an accessory and your colors can be green and purple

Outdoor ceremony

Here are some photos I found for inspiration. I wouldn't go too over the top with any theme as they can end up looking childish or tacky. In my opinion, the less is more theory applies to themed weddings.

Mardi gras is such a fun theme. i would definitely use purple and green as the wedding colors. and i would have some beads in those colors in the centerpieces for sure.

You could do a dessert bar with all those yummy New Orleans desserts. Mardi gras beads, umbrellas, masks, feathers, brass band music, and definitely purple, green and gold colors. And Pinterest. Pinterest will be your best friend.