Changes in consumer-grade photo quality between 70s/80s/90s are actually quite visible if you've looked at many of them. It's subtle, but e.g. newer ones have better range in brightness, i.e. less overly bright or dark areas in high-contrast images.

I got a bunch of Edwardian—WW2 photos in one go, and netted 3190. I might be able to get higher than that, but only if the photos predate 2000.

I think styles changed a lot from 1900—1970. After that, things are pretty hard to distinguish; retroactive clothing styles muddyvthe waters.

got 3632! and now my watch has ended

First time 2200.. what a fun game. I'll use your 2900 as a goal