Similar pages seem to only relate by colors.
Lord Tony, I must disagree very slightly. Although yes, 99% of them are colors and shapes, I have amazingly encountered about 3-5 instances where there were some actually related/similar images. Someone posted Spongebob freaking out to a mindforget video, and the Visually Similar for it showed lots of real similar ones. Then there were some images I put in that got different cuts of the image. It's not 100% crap, just 99%.
Also, the Visually Similar likes to default to Face checks, which can also get weird. You remember the searches I did earlier in the topic.