I didn't, but my sister did. It turned out very nice, and from what I could tell, no one could tell the difference between that and another self-owned bakery (however, you should not expect it to rival the high-end gourmet bakeries).
They have general set-ups and decorations, but you can also present your own ideas, add colors into it, or use flowers to decorate. What I would suggest is to just get a very plain cake, and decorate it using fresh flowers. It looks beautiful and colorful, but you can cut your cost down if you or someone you know feels confident doing the decorating.
Alternately, ask around in groups of people you know, or ask at a local hobby store, to see if anyone bakes and decorates wedding cakes privately. My stepmom's sister baked ours, and it was delicious, and beautiful. And cheap.