The nail-painting one can be used to be a bit ‘sassy’, so it’s like saying “don’t worry, I know other ways to find myself a bed for the night ;-)” but in a more nuanced way that I at least find funnier.

It’s probably not a universal meaning but my point is that emojis can be used to express more than just basic emoticon ‘UNIVERSAL EXPRESSION OF HUMAN HAPPINESS’ style things.