I think it's a great idea. Really good @#$!, if you will. I'm hoping maybe some runners-up (me, me - pick me!) will get a cool Twisted Oak T-shirt (you do have those, right Jeff?).
A creative contest is a terrific way to involve your fans in the spirit of your winery. Maybe you're not quite as wacky as the Twisted Oak folk, but I think this sort of a contest would work for almost anyone (even Harlan Estate or some equally lofty producer). I had a great time with the Anomaly Vineyards "crush T-shirt slogan" contest, and even though I didn't win, they sent me a T-shirt with the winning entry printed on it. Believe me, my suggestions were much more clever than "Cluster's Last Stand."
(But I'm not bitter).
This sort of contest is a reward for your fans. Hell, it *identifies* your fans. The trick is to involve as many people as possible. You might even let people vote on the top three choices. Or let them make the top three choices for you to vote on. And then, in some way, recognize/reward everyone who participates.
(Success has many parents, failure is an orphan.)
The best thing about the Twisted crowd is that they aren't afraid to try new things. And even if Twisted Oak is doing a contest, no reason you can't do it too. Their fans are probably not your fans. Way to go, Jefe.
Let me know about similar efforts your winery has made in the comments.