If you have time to make them you can have columns with fluting. I use the plastic corrugated roofing as the base and wrap it around plywood disks. The roofing provides a look which resembles fluting. Then create the capital of choice.
For 12 foot columns we used disks placed 4 feet apart and wrapped the roofing around them and secured with screws. For a rustic approach we wrapped it with gauze and then painted it. They were very effective. I have built sizes of columns from 8 inches to 2 feet this way and they are pretty stable. If you need to support scenery you can run a 1 by 4 or 2 x 4 and notch out the disks. I have used this method for supporting a second level for Lysistrata.