Asian Hunter,
I wouldnt have thought so just be mindful privacy is essential to the girls as well as the punters, it's probably better to look at whatever photos they have on their websites and read the feedback on UKP then enquire about a booking.
I would have thought you need to show you can be trusted with the agency and that your genuine first before enquiring about a face photo.
You can walk away from agency booking and I have, if the girl you have booked is not like her photo and it's not for you be honest with your self and sensible with your hard earned. Be courteous of course but, a 'sorry my fault booked the wrong girl' is a more positive way to walk.