My feeling is that you need to let users choose the demographic rating their photos. This clearly has a bit of a cold start issue though. I'd really love for

My feeling is that you need to let users choose the demographic rating their photos. This clearly has a bit of a cold start issue though. I'd really love for a service using ELO/relative ranking to exist and exactly for this purpose. I've used https://www.photofeeler.com https://www.photofeeler.com in the past - I think you're looking to give users a similar service. I have greater faith in your ELO method though. Perhaps to give you some motivation, I've paid over $50 for that service to get a feel for different profile pictures. I'll continue to use it too as I consider new photos. They have a slightly clickbaity blog, but it has some interesting posts like this one: https://blog.photofeeler.com/psychology-study-science-best-profile-picture-unbiased-strangers/ https://blog.photofeeler.com/psychology-study-science-best-p...