You could give Lay like a jetpack or something on his back

Whiskers

Its hard to do whiskers with his rhombuses on his cheeks

No offense but you kinda need to do that for all of your cat OC's.

I'm not really sure exactly what you could do but maybe try something with his tail?

Well Milo has that tuft on his ear, Ripley dead, Larrys dead, Violets dead, and sizzle and fry are never mentioned

So then that's Milo?

claws, and make his top half separated from his bottom like this ^

More like <

But idk, the line doesnt help, and the claws are very small

heres my idea

He looks deranged

But idk

the point is
the head should be more defined, and also should be on a swivel mechanism that allows him to look around

Ok..

I think the justification for no swivel is that the materials used to make lay are super flexible.

You could add some wires sticking out and maybe a more polygonal tail.

This is gonna sound really weird, but...
Robot arms on his back
(Sorta like Doc Ock but not as imposing)