The problem with ANSI in present day, present time is that you really need to go out of your way to display it, because it's not well supported by modern software (unlike in MS-DOS days, where it was default), so, I'd stick with ASCII (with colors, optionally) if I were in your place. Or… is there such a thing as UTF-8 art?
Be a l33t h4x0r and write your own drawing tool. It's easier than even making a proper text editor. All you need to begin with is a rectangle character grid and a moving cursor.