Workers' compensation has a lot of nuances and varies state by state, but here are some basics. This insurance covers employees on payroll who receive a W-2. It is not meant to cover volunteers or individuals getting paid as independent contractors. That said, if an independent contractor working for you is injured and does not have a workers' compensation policy in place then your policy should extend to cover that individual.
It is very important that you ascertain whether your people are independent contractors or employees! Many people get fined by the Workers' Compensation Board because their "independent contractors" were actually employees. According to the IRS:
The general rule is that an individual is an independent contractor if you, the person for whom the services are performed, have the right to control or direct only the result of the work and not the means and methods of accomplishing the result.
For example, if you said to a assistant working for you, "A gallery wants to have ten versions of the blue and turquoise necklace that we designed last week. Can you make the pieces and deliver them to the gallery by next Thursday?" (i.e., the assistant is responsible for solving the problem on his or her own schedule up until Thursday's delivery date), then that person is likely an independent contractor.
However, if you scheduled studio time and set out a schedule for how and when each piece would be finished that you required the assistant to follow, then you are now in control of the "means and methods" of accomplishing the work.
If you are not sure, don't risk it: consult a lawyer who specializes in employment issues. The safest choice is to pay people as employees and get workers' compensation to cover them. Fines of $65,000 and up are not uncommon; in contrast, this policy can cost as little as $250.
I don't just have people that I pay, I have lots of volunteers. Now what? PAGE NOT FOUND: volunteer-accident
I know all of this and I have crazy amounts of coverage. In fact, the Department of Labor is my friend on Facebook! But I did just invest in thousands of dollars worth of wool, fabric, and sewing machines. You need property coverage. Property Coverage