In the bath (although there are bubbles, part of the baby's er anatomy are clearly on show. I wouldn't feel comfy posting pictures of my DS like that, although I know from speaking to MIL that she has no problem with that sort of picture and finds it cute. My own mother is very, very cautious about what goes on FB, too much so IMO so it can go either way!
A friend posted a picture of her DD, wearing nothing but her knickers (she was older than 3 at the time), which I found...odd. Yes, it was hot, yes it was summer and yes, DD was possibly far more comfortable wearing nothing than she would have been wearing clothes. But IMO that is for them to decide behind closed doors and I just personally wouldn't do it.
I have posted 1 photo of DS when he was in the bath, aged about 6 months old, it was his first "proper bath" with loads of bubbles etc and really all you could see was his face. I dilly-dallied for ages as to whether or not to post it at all and when I did, I was paranoid someone would complain and get it taken down, innocent though it was.
IDK maybe I am being a little over paranoid!
(We are in the UK, and it is not usually anywhere near hot enough to want to run around with no clothes on! When it is, it is something to shout about, which is probably why we Brits talk so much about the weather!)