I did consider something similar, electroluminescent, layered 'stickers' that you can design yourself and they light up various colors.
Hell, you could probably make it display something useful like temps, but there are two hurdles:
- it's a bit involved, difficult to make and easy to damage. Any small tears effectively destroy them.
I'm suspecting the reason it's not done with a computer case, is because it's so easy to achieve the same kind of effect with LEDs diffusing light through glass or plastic in the context of a computer case. If I saw a case covered with this, I'd probably just assume they had done something fancy with LEDs if I didn't look closer. Seeing a computer case light up or glow in the dark is not really surprising at all, and there's just not enough surface area on a computer case to justify using paint instead of LEDs in most cases.
To me this looks like a scaled-up version of what gamers are trying to do with all that RGB/LED lighting all over everything. I mean, I'm not saying it's a bad idea, just that it wouldn't stand out as much in a space where people are already into using electricity to make stuff glow in the dark by other means.
I do admit, it would be cool to see it used to do things LEDs can't do as easily, and to see the look on someone's face when they think they're just looking at another typical LED setup, for them to realize it's paint.