Not something from my childhood bathroom, but a couple of curiosities I've seen in other people's bathrooms:
Lots of framed photos of the family's very sporty daughter in various teams: swimming, netball, hockey, etc.
And I think this beats them all, which I saw in about 2005, which I have never seen anywhere else. A glass toilet cistern which doubles as a fish tank. Yes, really, I kid you not! It was carefully designed (probably custom-made) so that the fish are not sucked out, and it only emptied to about half-empty, when the toilet was flushed. I asked if the fish seemed bothered by this regular disturbance: I was told that those fish lived longer than any others they had had.