Étang en Ile de France by Henri Biva, RGBA8888 PNG-32
618 KB, 534 KB after pngout optimization

Étang en Ile de France by Henri Biva, Indexed PNG-8 with DawnBringer Aurora palette and noise dither
191 KB, 128 KB after pngout optimization

Étang en Ile de France by Henri Biva, indexed PNG-8 with adaptive palette (threshold 400) and noise dither
234 KB, 190 KB after pngout optimization

Mona Lisa by Leonardo da Vinci (color remastered), RGBA8888 PNG-32
394 KB, 338 KB after pngout optimization

Mona Lisa by Leonardo da Vinci (color remastered), indexed PNG-8 with DawnBringer Aurora palette and noise dither
136 KB, 84 KB after pngout optimization

Mona Lisa by Leonardo da Vinci (color remastered), indexed PNG-8 with adaptive palette (threshold 400) and noise dither
180 KB, 123 KB after pngout optimization

And some novelties...

Étang en Ile de France by Henri Biva, indexed PNG-8 using Mona Lisa's palette
209 KB, 134 KB after pngout optimization

Mona Lisa by Leonardo da Vinci, indexed PNG-8 using Étang en Ile de France's palette
128 KB, 80 KB after pngout optimization