Just my two cents in the whole similarity discussion: not a proposal, just a reflection about it and some possible practical ways out of it. It's just that lately I noticed 2 batches of similar images can be very different regarding their similarity ;-)
The hardest thing won’t be applying this to future submissions, but to get rid of the ‘historic’ similar uploads…
Here we go ;-)
1.Are there duplicates in this batch of “similar images”?
YES → limit number of duplicates to one image; tell the contributor not to submit duplicates ever again and to behave like a good boy or girl from now on; go to step 2
NO → no actions in this step; go to step 2
2.Are the images strictly subject-related similars without any concept attached to it? (for example: landscape, same building or food dish taken from 34 angles, the same isolated object, illustrations of the same subject with minor color changes, model shoots with no or minor differences in angle nor background nor concept)
YES → limit SUBJECT-similars to 3 distinctive images; go to step 3
NO → no actions in this step; go to step 3
3.Do the images share the same concept or feel but don’t have the same style or appearance? (for example: “going to the dentist”, “clean environment”, “seductive looking woman”, “retirement”)
YES → limit CONCEPT-similars to 5 distinctive images; go to step 4
NO → no actions in this step; go to step 4
4.Do the images share the same style but with different subjects/concepts (same model, same setting, same lighting, but with different concepts or expressions / isolated objects / graphical or near-graphical lookalikes but with completely different subjects and/or concepts)
YES → limit STYLE-similars to 20 images, no limits for isolated objects; go home, relax and be kind to everyone.
NO → you have been a fool to waste your time on examining this batch, there were no similars to be found here in the first place ;-)
Step 1 is obvious.
Step 2 in order to prevent 30+ images taken from 30+ slightly different angles of the same plate of celery soup or the same lame office building or the same model, however good-looking she or he is.
Step 3 in order to limit uploading of images with a green-minded model with an apple in her hand (same model, same apple, but different angles, poses or backgrounds). Or limit uploading illustrations of a robot walking to the dentist with a clearly aching tooth (and passing the bank, the office, the bakery, the supermarket, the garage and whatever before reaching the dentist)
Step 4 in order to encourage striking styles, but with very different subjects or concepts. Like these ones:
Well anyway, just of few thoughts of mine.