"Broken glass floor - great for a bathroom floor or countertop. Just lay broken mirrors on the floor and top with polyurethane"
I don't even know where to start with this one. That's not what this is an image of. The image quality makes me believe it came from a magazine of sorts, but I'm having a hard time finding the source. My first thought when seeing this image is that it was an artsy spread of some sort in a magazine, not some great DIY home design project.
I'd like to point out there is no sealant or polyurethane in that photo, it's just broken mirrors. Also, as someone who has done a lot of refinishing including the floors of my house, polyurethane is an extremely thin sealant - I think what the creator was the pin was thinking more of would be an epoxy resin, which on the floors wouldn't work easily, takes days to set up, and bubbles like crazy unless it's set just so or with a heat source.
So yeah, this isn't even doable if you ask me, at least not as a DIY home project.