P411 has a feature for clients to attach a photo to their profile. Providers:  
1. Does anyone really do this?
2. Would a picture help your screening process?
3. Is so, what kind a photo would you want to see?
     Clothed, Partially clothed, Nude
     Full Body, Waist Up, 3/4 body

1.  Yes, some guys do.
2.  No, not really.
3.  If there is a photo, you better not be naked.  I really don't want to see your junk in a picture.  
And don't send my email photos with your junk hanging out either.  Clothed with your dog is nice but  
really not necessary.  
Thank you.

Do guys actually show their faces in those pix?

But most don't & I like surprises. ( good ones that is)

Some guys do. And yes they show their faces. This has no impact in my decision to see someone or not. I would not allow or deny based on a pic.

Whew. I sometimes worry that my gigantic muttonchop sideburns fail to distract attention from my grape-sized nose wart and inch-long lower bicuspid snaggletooth.

I did at one time have my pics up then I took them down. The thread below is a good reason why not to do it.

Hee Hee Hee,  I'm usually anticipating a dicky-do and a hockey mullet  

There's no good reason to put your picture up like that.

But that's very rare. And a face shot isn't needed. Can always cover it up somehow. Watch the distinctive tats also.

Is if I am doing an outcall and I can match the pic to the face upon first meeting but really not necessary.  

I don't want to hear anyone talking about how bad it is that ladies don't post face pics.

1) absolutely, and I appreciate it. Why? For the simple reason it shows he is being forthright. Please look at it this way: a potential client can view a ladies photos, and read all her fictitious stories on TER and other places. Uploading a photo on your p411 client account is a nice gesture, IMO. As is emailing one without being asked.  
2) it is possible, there are many variables- an online presence would be my reason to use it for screening.
3) a casual candid, or your business profile photo. Clothed. Full body not necessary, it is not a determining factor for me.

I'm pretty new to this (started in January), and I had my picture up there for a while.  A few months ago I had a provider tell me it's not a good idea, so I took it off their site.  It was nothing special, just me sitting outside in a neat location (fully clothed, btw), and it did show my face.  I did not leave it turned on all the time, only when I had sent a request to a provider.  The rest of the time it was not turned on, so no one could see it.