If you type the word "porn" into google, you'll find lots of pictures of pretty ladies wirh no clothes on. And its free
But seldom, if ever, ones of the WG you're thinking of punting that day/afternoon/evening.
I always regard face pics as a bonus, but I usually like to see pics of her naked, as a taster, as insurance. I'm far more likely to book a girl if I've seen a photo of her naked. Not necessarily open-leg, axe-wound shots but certainly a standing up, full-frontal shot. Better still if she knows how to pose and doesn't just stand there like a sack of spanners.
Beats me, though, why some girls have naked pics freely available, but a PG full of 'NN' pics.