Upscaling with a neural network resizer such as Topaz Gigapixel Ai dramatically improves the usability of the art. On1 also has a resizer that might be a good less-expensive choice.
I'm imagining a variety of different tools to improve the images, so ideally if an image is good enough for somebody, they could "enhance it" and from then on, that image would be available at a higher resolution for all users.