Marowak: "A Marowak is the evolved form of a Cubone that has grown tough by overcoming the grief of losing its mother. Its tempered and hardened spirit is not easily broken." That's pretty much Normie, without the ferocious temperament.
Banette: Not only is it the pokemon that most resembles the venom symbiote, it's also got a similar backstory of how strong feelings of hatred turned it into a pokemon. He probably got it while it was still a Shuppet, though, as Shuppets are attracted to strong feelings of vindictiveness, something Normie had in spades during his brief stint as the Green Goblin.
Murkrow: It reminds him of his fiancee, Brenda, who is a costumed hero known as Raptor.
Spinarak: It's a green spider. How could he not?
Klang: He likes to build stuff, this is pretty much the visualization of building stuff.
Sylveon: It's really, really cute. He likes the soothing aura it emits.