I'm going to be blunt here because I'm in that mood today, but this is how I feel about it.
You had SEX. You got PREGNANT. Now they're coming to celebrate the baby and bring you gifts for when you push it out of your VAGINA.
Body parts should not = embarrassed anymore LOL
I don't think nipple cream and nursing pads should be left off the registry - you should know what you're getting into if you get invited to a baby shower LOL
Besides, you might end up getting a few different brands (although I'd go with washable, everybody says the disposable end up costing an arm and a leg...) and have ones for different uses and different cup sizes, since that can vary.
My only concern in having nursing pads on the list is that some women have to buy them early... Like my BFF, who is leaking on a daily basis in her 2nd tri - she isn't going to register for them, she's buying them this week LOL
GL hunnie! And don't be afraid to put anything on your registry, except maybe the big overnight pads - those might be a little too over the line. But everything else - go for it! If people think its gross, most people are too nice to say anything and just won't buy it.