I just took me pajamas because I knew I wouldn't be up for much more. I also took him a couple sleepers but they provided one also that I let him stay in a lot so I wouldn't have as much laundry when I got home lol
I was there for 4 days. I would bring sleepers and onesies, socks, mittens if necessary and hat. My hospital had a lady taking professional pics too. So if you're interested in that I would say an outfit for pics too.