You can add breastpump, bottles of your preference. I enjoyed perfecting my baby registry and i had like 35 items on there all of which i really need. I didnt like adding things i can get for free. I have gotten almost everything free so far which is really cool and easy to do (if your ok with used items).
The best thing i got was a boppy pillow. Not an essential but it has a lot of uses. Also put safety items on there. If u go to babies r us they will set u up with a checklist, packets, magazines coupons and let u walk around the store scanning everything you want! You can add or delete stuff online too
Diaper bag, every size of diapers (you can never have to many), wipes, bath supplies (soaps, mostly), travel system, baby monitors, & a health & grooming kit (i think they usually come with a thermometer, nail clippers, medicine dispenser, brush & comb.) Of course some reciving blankets, & mittens so they don't scratch their face (or you can get the onsies that come with the mittens attatched) honestly if I were you, I'd go ahead and just put everything on the check list on your registry. You never know what you're going to get and what you're not.. I got mostly clothes for my shower anyways, and a couple packs of diapers. You can never have to much on a registry.