If I ask for a photo: I usually call the provider first. Tell them the situation, and introduce myself for verification. For example, if the provider is a TER member, I can PM the provider for a pic. Most of the time when I ask for a pic, its usually a face pic cause the providers profile does not show the face pic. If she's not comfortable with that idea, then I have to take my chances with her. It makes me feel more comfortable to see who I will visit.

For others, they may blatantly ask provider to send them pics over the phone, request inappropriate pics, and without introducing themselves for verification--that may be a red flag for many providers. Again, I may call the provider and explain my situation and let her verify me, or I may e-mail the provider with the reasons mentioned above. Hope that make sense?

... I can understand a request for a face pic.  Some ladies have fabulous bodies and Indian Chief's daughter faces.  If the pics posted are "glamour shots", then I can understand a gent wanting a recent candid pic. Photoshop can take 25 years and 25+lbs off.  There's no harm in asking...

However, just because I can understand where the guy is coming from when he requests these things does not mean *I* am willing to provide them.  Once a pic is sent, I have zero control over what is done with it.  The gent may simply be adding to his 'spank bank' or he may have some deeper, more disturbing MO.  Even in the case of a harmless gent, he may be less than diligent in hiding/deleting the pic and there can be repercussions from that as well.  There are plenty of pics of me out there (professional, watermarked, face blurred) and plenty of reviews for him to read between the lines with to decide if he is willing to take the risk in seeing me - *without* my having to give him even more visual enticements.

-a 13 y.o. computer nerd who needs new inspiration for his wanking sessions or a much older but equally sad picture collector weirdo. Neither is getting my photos.
-another provider or agency trying to get photos fro their B&S scam
-the usual time waster who could be anyone really but no intention to book b/c he was too lazy to read my reviews, each of them stating that I look exactly like my pics.
Either way the request is deleted.

reviews link.
skb

I've never asked for a pic or had a reason to ask for a pic.  Some legit or nearly legit reasons (NOT applicable to you) are:

From following ads for a while, maybe he knows her pics are outdated (I could name a few!). Even if they are still accurate, he might ask for a recent pic, even just a phone cam pic with "proof": hold a piece of paper with this (secret phrase) on it, pose a certain way, or something like that.

If there are many good reviews but a couple of recent reviews take a turn downward he might ask for a recent photo cam pic.

Other reasons are common but less legit or not legit at all, IMO.  
Blurred face: reasonable for him to ask, but completely reasonable for her to refuse.
Nude pics: forget it. If you don't know who it is, it could be a minor and you've contributed to their delinquency with your emailed pic.