Every once in a while I get a dirty room for whatever reason. Best response is definitely to immediately head back to front desk and ask for a replacement. Don't bother taking pictures.

On the other hand, sometimes I return to my room after a day of work and find it hasn't been serviced, in which case I've let the kitchen guy or whoever is around do the minimal job, at least getting my bed made and the towels replaced. Although they're usually not as good as housekeeping, it's my own mess and not some stranger's.

I'm usually nice, but insistent, and don't ask for compensation in these cases. The result is that they usually act apologetic, rather than defensive, and offer me something like a free meal or 10k points. Mistakes happen.