Snickerbobble
The Painter
Lenses:
Like you said, with Terraria's light system these would be useless at the moment. I also doubt their usefulness if light could be directed unless you're thinking about powering certain blocks like spark gems with them and make some interesting... I dunno... powered blocks.
Anyway, this all seems too complicated/not thought through enough for me.
What if a lens is placed on a gemspark block, it will emit a beam of light across in the direction? With the different gemspark blocks, there would be different beam colors, and through wiring you could turn them on/off. Could make some cool lighting effects with this, I think.