I like the textures you used on this, the tile looks very realistic and the cube itself does appear to be made out of some kind of steel or marble-esqe material. A couple minor details stand out to me though, the tiles appear to be perfectly cut, so that if you rubbed your finger along the long edge of one you would likely by cut. I think the tiles would look more natural if they were rounded along the edges. Also, the hearts on the companion cube are solid pink where the rest of the cube is a mixture of textures. If you could mix the textures together so that the pink flowed with the textures of the rest of the cube, I think this would be an ideal background

You know what would be really cool is if the pink lines on the cube actually glowed pink, now that would be neat

Also, the lighting seems a tad dark; like it's leaning more towards cloudy day than the florescent lighting I think you were going for...