I like @PearsonArtPhoto's answer, though the considerations about exposure time may not be correct. I was looking for something more visual.
The website states an area of 0,53m² of the Van Gogh image, and since the original is 92.1 × 73.7 cm², the large version must be about 0.817km wide.
During his year in space, Scott Kelly took tons of photos, one of New York from straight above at night. And Central Park is about 4.07 × 0,86 km² in size, which means its small side is roughly as long as the long side of the Van Gogh.
So here is the picture from Manhattan with the Van Gogh above Central Park. The Van Gogh was scaled by a factor derived from the size of the original, of Central Park in reality, and the pixel size of Central Park on the photo, so it's quite exact. (Width: 105px)
I blurred the right one until I felt that its sharpness is about the same as that of the entire image.
Finally, I cropped the picture to the interesting area, but didn't scale it.
(Source of original: https://www.nasa.gov/content/best-year-in-space-photographs-from-scott-kelly)
What's quite interesting now is the EXIF data of the photo:
- It was taken with a Nikon D4, making photos of 4.928 × 3.280 px² (16.4MP) with its full frame (36mm) sensor. The size of the original photo is the same, so it was not cropped or scaled.
- The lens was a fixed-length 400mm f/2.8, and the photo was taken at f/2.8 to collect as much light as possible. Note: A higher aperture of may be f/5.6 collects less light, but would give a sharper image. (Though this effect should be low for this lens).
By the way: Assuming an altitude of 400km, the width of the Van Gogh should be 112px, which fits my 105px quite well. So, no teleconverter was used!
- Exposure time was 1/8s, during which the ISS moves about 1km. But there's absolutely no in-motion unsharpness in the Photo, so the camera tracked the motive very well.
I'm wondering, because usually it's very difficult to shoot a sharp 1/8s photo at 400mm when holding the camera in your shaking hands. Such lenses have image stabilization, but this doesn't work nicely when you have to track the motive. May be, zero gravity and the weight of the lens helps a lot. Finally, the photo was processed with Photoshop, and some unsharpness could have been removed.
So, the Van Gogh is about 100px wide when photographed with a 400mm lens on a 16.4MP full frame camera. If the ISS has a 800mm and a converter to get 1120mm, it would be 200px or 280px wide. If a camera with APS-C sensor is used, the width increases to 448px, and if this has 24MP instead of 16MP, the width would be 546px.
However, sharpness of a lens is limited. You can't increase sharpness by using smaller and smaller pixels. While I think you would get a sharper image with the 800mm plus teleconverter, you would not gain more sharpness with an other camera.
Playing with the numbers, the Van Gogh would still be small compared to the entire photo size, but large enough to be noticed. Sharpness is limited, but looking at the level of detail of the photo, the Van Gogh should be recognizable even when photographed with a 400mm lens.