Images as in "pictures" or is that something else? I'm using Alacritty, and I don't think I've once thought "I need to see this image inside the terminal" and I do deal with images and frames from videos a lot. Probably if I saw it being added to Alacritty I'd think it was adding unnecessary bloat, so I wouldn't be surprised not every terminal is rushing to implement it.
Or I completely misunderstand what you're talking about.