You already know how obssessed I am with this myth. What a great choice! You’ve already defined the perfect mood for this pair and I’m curiuos to see what your concept for the background will look like.
I’m with Melissa in saying that Persephone needs to be softened up a bit to contrast with Hades, but another way to look at it is perhaps she’s been ‘acclimated’ to Hades environment? I’m sure that some contrasting color schemes will help the pair out too.
If you DO go more inhuman and robotic with Hades, I’d love to see how you do that! Maybe some funky cyborg bits in various places? I can totally see him with mecha legs.
It’s gonna be grand fun! Keep it up hon!