Err, most of these are not naturally occurring pairs since in each case the images differ by a human manipulation (resolution reduction, drawing an arrow, changing the watermark, changing the aspect ratio)---which I'm guessing is viewed as a feature not a bug by the designers of this system. The axe and the nematode comes closest, and even then, they are low-res and visually similar. What would be far more concerning is a hash collision between a picture of a piano and a picture of an elephant, but nothing like that is happening here.