The light type is simply the most horrible excuse for a type idea I've ever heard. There's absolutely nothing in that idea that couldn't be done using another type. If you mean light as in the sun, light bulbs, etc, you have the fire and electric types. Light as in "holy" a) provides very few ideas for new pokemon and b) is mostly covered by the psychic type.
I see almost no justification for this type. All I see is "it'd be an opposite to the dark type".
a) Dark = sneaky/evil, we've established that.
b) Since when does Dark need an opposite? Hell, since when has any type, ever, had a proper, polar opposite?
I'm putting in a vote for the Digital type. Unlike the light type, it opens up a massive new niche. Pokemon that fire waves of digital energy, viruses, blasts of radio waves, concentrated electronic signals that fry your brain. Who's gonna tell me that's not awesome?
I'm not even gonna talk about the "Wood" type. Some people must have parts of their brain missing....