You can go a bit further to get significantly higher color depths using ASCII block characters 176, 177, 178. By using the foreground and background ANSI colors and blending them by using these three characters (25%, 50%, 75%) you can achieve some quite realistic images. If you're more interested in resolution, using half block characters like 220 and 223 can allow you to double your vertical resolution at the cost of not being able to use the color trick.
I made something similar to this using a combination of 256 color mode and unicode halftone characters for "dithering" between the foreground/background colors.
Another thing I'd like to try to get a bit more resolution is to perhaps use the braille character set in combination with 256 color mode: https://github.com/asciimoo/drawille
Also, some terminals are starting to support 24bit color (iTerm2 nightlies) which could pretty drastically improve the possibilities of terminal based video: https://github.com/frytaz/txtcam/tree/color :)
I've tried doing this before but wasn't fully satisfied with my color lookup (very basic - really, even a hash table would do the way I made it..) https://github.com/minikomi/ansipix
Do you have any good examples of calculating the right foreground/background colors to use?
