I get what you are saying...
In my case, I can usually tell what hits are bots hits by just looking at the time and frequency of the hits across a wide array of images. Most of what I am seeing is not human.
Carry that one step further... On my custom domain which is only a few weeks old, which has basically no image search ranks, and zero backlinks other than a few here on the forum should be getting very little traffic and Google Analytics concurs. I have not yet even began to market it or use it for linking.
But yet, I see a ton of automated traffic. Only 5-15% of which is real humans.
Cheers