I think the fallacy is that choice is a negative. Especially if done properly choice can motivate a buyer to purchase. While having the same exact work on your site might hurt depending on the caliber of work, other genres would give the consumer a broader idea of what they truly want. If you do not make pottery but know of a great pottery artist, why not help the consumer find what they want and then you both succeed. That is what an affiliate relationship does it benefits both parties. You get a commission for the referral and the artist gets a sale they might not have had without the traffic from you. That is capitalism, it promotes you to work harder and everyone else to work harder for a better product for the consumer. Right now it is not something I have even tried but I believe that with the right factors it could work.

"I think the fallacy is that choice is a negative."

No the fallacy is that a multitude of choices will encourage a purchase of YOUR particular product. Yes when you go into a Supermarket you are more likely to buy something when it has a range of choice than only a tiny selection. But you buy that piece that catches your eye. In which case, have many choices muddies the water for the seller. You are another bottle on the shelf.

"Not if you get a agent that's a friend or is just handling excess workload for you."

Well that sounds more like a manager than an agent. In any business, you can break it down into three sections, Production, Management and Sales. People who make the product (Production), people who handle all the tasks needed to run the business (Management) and people to sell the product (Sales). A manager would be handling all the administrative tasks needed to run a business. This would be very useful since it would allow the artist to focus on making their art (Production) rather than the more tedious tasks of ordering art supplies, paying the bills, keeping the books straight, etc.

An agent on the other hand, would be for Sales. You wouldn't want an agent that couldn't bring in new work on a regular basis. Nor would you want one that would be handling the management part. Their job is to hunt down new clients. Getting an agent makes a lot of sense if they can get you into markets that you wouldn't be able to get into otherwise. They would more likely require to be the exclusive representative of your work in a certain market or geographic area. Like most sales people, they'd be working on commision. So they would always get a cut of the action.

Of course, whether you get a manager or an agent depends on what your business really needs. If you already have more work than you can handle, a manager may be best since they can help run your business, freeing you up to produce more work. If what you need is getting more work, than you should be looking for an agent.