https://hpjansson.org/chafa/
Hadn’t heard of Chafa before.
Chafa supports outputting to all popular terminal graphics formats according to the Chafa website: Sixels, Kitty, iTerm2, Unicode mosaics.
Speaking of which it is also worth to point out that for example sixels were first invented and put into use quite early on:
> […] as a way to send bitmap data to the VT200 series and VT320 terminals when defining custom character sets.
https://en.wikipedia.org/wiki/Sixel
In the references if that Wikipedia article you see for example VT330/VT340 Programmer Reference Manual, Volume 2: Graphics Programming from May 1988.
https://www.vt100.net/docs/vt3xx-gp/chapter14.html