Apart from all the other aspects - is the picture even a good testcase? I'd assume there are probably far better test images to use when evaluating. Why not us

Apart from all the other aspects - is the picture even a good testcase? I'd assume there are probably far better test images to use when evaluating. Why not use those? If I were to design an algorithm working on images, I'd make sure to test it on the best test cases I could find, exposing flaws and strengths.