Every picture of me from when I was under six or so shows me wearing nothing but panties. Mom says I just never wore clothes (except when we went somewhere) until I started Kindergarten. She didn't think of it as a big deal since I didn't "have anything to cover" anyway

DD is a lot like this, and we've gradually introduced new clothing rules as she ages. Honestly, I don't think it's a big deal for her to be naked (except for undies, which are a must around here) until she starts developing, but I wanted to start addressing it earlier so she wouldn't feel ashamed of growing breast buds, etc., and so we could make the transition more gradual.
Each time we have changed the rules, we've explained that it is because she is getting more grown up and needs to act a little more grown up about some things.
At 2 years old, she was told that she needed to be covered in public. (Our version of "public", which is used for a few different rules, includes having company over.)
At 3 years old, the rule was that she needed to be wearing panties (or some kind of bottom other than a skirt) unless she was in a room by herself or she was bathing/showering.
At 3-4 years old, she was told that she was getting too big to shower with her Dad (but she could still shower with Mom).
At 5 years old, the rule was that she needed to be wearing some kind of top in addition to her panties... anything that covers her nipples is okay. (At this point she began insisting that her dad also wear a shirt, since he runs around in his boxers or just shorts at home sometimes. We agreed that was fair and Dad now wears a shirt of some kind at home too!)
She is still allowed to sleep -- and cuddle with me before sleep -- wearing nothing but her panties. I take off my pants to facilitate skin-to-skin contact (she likes to throw her bare leg over my bare leg), which she still craves before she goes to sleep, but I leave my shirt/bra/granny panties on.
I figure when she's 8 or 9, I'll start expecting her to wear a dress/pants/skirt/shorts at home, because I suspect DH would get uncomfortable if she's running around in a tank top and panties when she's developing.
Maybe not a lot of use to the OP, but that's how we handled it.
--K