Depends on how long the dress is and how comfortable you are with your calves and feet. 🙂
Pardon me for geeking out for a minute, but I used to work at a clothing boutique and got questions like this a lot. One option is to go barefoot–natural and delicious, but you have to be pretty sure you’re not going to step in manure (unless you like the feel of it between your toes–hey, to each her own) AND you have to be comfortable with lots of people seeing your feet.
Ballet flats in a contrasting color could be adorable with a dress that’s above the knee or tea-length, although with a tea-length dress I’d probably recommend a modest chunky heel (the thicker the heel, the less likely it is to sink into the ground and/or snap in a hole). Peep toes can be really cute with a shorter dress, too.
What you want to avoid (besides the obvious ankle breakage) is anything that makes your lower body look segmented–the classic Ugg boots-bare knees-mini skirt combo that was so popular in my area around 2007 comes to mind. The overall effect is that the boots, your visible legs, and the skirt are all the same size (at first glance, you see a stripe of skirt, a stripe of leg, a stripe of boot). Unless you’re very skinny and have very long legs, it’s not flattering.
That being said, a good pair of really distinctive cowboy boots could be distracting enough to make the “boot-leg-skirt” stripe illusion go away. 🙂 Bedazzler and puff paint to the rescue!
You could also consider changing shoes at some point during the day–if you have two pairs you love, wear ’em both! It’s your wedding! Switching shoes will also stave off some sore feet in the later part of the day. You might want to consider getting some of those cheap gel insoles, whatever you do, because you’ll probably be on your feet most of the day (unless you’re wheelchair-bound or getting carried around on a litter by burly men… which would be awesome)>