Since I upgraded to 33s within a month of buying mine, I left the spare on there until I finally needed new tires and of course I needed the spare right before I got the new tires. So it looked a little funny since it was a smaller diameter.
It was the original, it was 7 years old, so I took the best looking 3-year-old tire that I just took off and put it on as the spare. It's still nearly bald, but diameter was still a lot closer to the new tires than the 7-year-old stock one that had a ton of tread life.
Slight down side, the wider 33 now hangs down lower.
Although I did find a narrow tire the same diameter, I'm sure it'd tuck up out of the way nicely. But I'm not paying that price for a damn spare...