It's "voller" no matter the gender of the word following it? Since "Licht" is neuter, I put "volles Licht" and was marked wrong. Fair... but what grammatical function is "voller" invoking here to cause it to mean "full of"? A bit confused on how this works.
It's "voller" because it's a different case: It's "being full of what". When you write "volles Licht" it means "full light", i.e., the that the light is full. E.g. if you write "Sie ist volles Licht" it means "She's full light".
It could mean very pretty or very optimistic. I'm searching and nothing solid is popping up. It keeps trying to bring religion into the picture. Otherwise, I don't think it has a strong societal meaning. It's not common.
It would probably rather be lichtvoll than lichtSvoll - but that's not a word that I've ever heard. You could probably use it and people would understand what word you constructed, but I would have no idea what you are trying to tell me.