I'm all for theatricality, but looking at the practical side - as a metal band, you're probably gonna be playing a lot of multi-band bills. Try to avoid props which will require a lot of time to set up, take up a lot of room on stage, or require massive cleanup.
That means an 18 foot Stonehenge is not a good idea. Make it 18 inches for practicality.
That means an 18 foot Stonehenge is not a good idea. Make it 18 inches for practicality.