I moved PoemYou away from being a hypothetically useful greeting card service to being a completely useless ephemereal link stash. With five embedded media items in boxes and no history of previous items held in them. I sort of like the feeling. And it only works on Safari and Chrome. Because CSS 3D suffers from the browser 3D engine problem, namely that browser devs aren't very interested in being 3D engine devs. And the same goes for most sane web developers.
Still, it's got some cool cloud effects on Safari. The clouds are stretched 64x64px divs with gradient fills and low opacity. The effect looks surprisingly okay and performs alright.
But where to go from there. I could make it into a blogging platform. Give every user a box. Let them put something inside it. Have a page with the boxes of the people you are following. Have a birthday every day opening your new presents.
For mobiles and non-CSS 3D devices, I'd like to turn the boxes into letters or something equally... flat. I think you could still make some nice reveal animations for them, maybe a PNG spritesheet or three.js canvas renderer. Or pre-render the frames into a spritesheet. Anyway, the reveal, the reveal, it's the deal.