I see an opportunity here. A website who wants to curate products could use Etsy to locate sellers and convince them to list on their site. That curation website could develop a "stamp of approval" brand and grow that way. The art seller could include a printed note in the delivery saying "find more products like this on this xyz site". That way you use Etsy to draw in new customers but keep them as repeat customers for other products on this curated site. The main idea being that the curated site would not have to spend nearly as much money on advertising that Etsy does. Might work.