$1000 worth of art is a lot, so getting that paid back with art will take time. Yes, it is the artist's the responsibility, but if you want to see that art, it might be best to be proactive in this and set up a Google document listing each art piece that was agreed on with it's price and share that with them. Make sure only you can edit it, and state that with every completed image, you'll mark it as complete and the artist can work off the list in whatever order they desire. That should boost their art drive if they can choose the order from the list.
Good luck getting the art. At least the artist has reached out to you at all, right?