Chiyuki committed suicide by slashing her wrists. Where does her dummy body start to peel off first? At her wrists!
When Decim starts crying in the final episode, Chiyuki brushes away his bangs, revealing both his eyes. By removing his bangs you get rid of the mysterious and supernatural part of his character design, making him more "human". It's also symbolic of how he can now see with both eyes, as in seeing two sides: the arbiter side and the human side.
In the last episode, when the illusion of the real world breaks, it disintegrates into coloured shards. Memories are depicted as coloured little pieces of glass.
Decim and Ginti test Chiyuki and Mayu in a similar fashion; in exchange for someone else's life, someone can be saved. Although they both believed the arbiters (it's safe to say they were lying), Mayu "failed" the test. It seems the correct decision is to selflessly refuse the offer.
There's a particular species of jellyfish, Turritopsis dohrnii, which when heavily stressed can revert back to a polyp state and regrow itself, essentially reincarnating. Quite fitting, then, for a place where souls can be sent back to be reincarnated to have a large aquarium filled with jellyfish and a huge chandelier that resembles a jellyfish.
Misaki's assault on Yousuke in Episode 4 becomes rather more disturbing when you learn that, typically, arcade machine screens are made of reinforced glass to prevent damage done to them. Misaki managed to smash Yousuke's face into the screen so hard glass was embedded in his skin, and even she was surprised at this! Never underestimate someone when they're highly desperate, not even yourself.
, which when heavily stressed can revert back to a polyp state and regrow itself, essentially reincarnating. Quite fitting, then, for a place where souls can be sent back to be reincarnated to have a large aquarium filled with jellyfish and a huge chandelier that resembles a jellyfish.