NES Palette Converter - 8 Bit Image Maker

The NES generated colour directly in its picture processing unit rather than reading from a palette in memory, producing a fixed set of roughly 54 usable colours with a characteristic muted, slightly washed quality.

It is by far the widest palette here, so it keeps far more of a photograph intact than a four-colour set. Floyd-Steinberg suits it well: with this many colours available the error stays small and the grain stays fine.