I did look into that, but it's not as widely supported as the UTF8 half-block.

With many bytes necessary to print just six pixels, it wouldn't be as low-bandwidth, right?

On the other hand, how about libcaca? https://en.wikipedia.org/wiki/Libcaca

The TTY "graphics" rendering is actually relatively trivial, it's really just a few lines of JS in my rewrite now. So there's no need for an external rendering lib. Also with the new approach, I'm focussing on real text as the main feature, so you'll actually be able to turn off the colour blocks and just surf the web as raw text, with all the goodness of full CSS rendered, realtime text and JS.