When it comes to paid ads sites Eros & TS4R, I can attest that they do do due diligence when it comes to "Verified" or "Authenticated" ads. An example. I've been authenticated provider on Eros for 5 years, but if I submit a photo that only shows me from behind, they won't post it unless I submit to them another photo from the same shoot showing my face. I can't speak to how far those sites go to verify all pics for non-authenticated/verified providers (although even those providers have to submit both a face pic official ID plus a current face pic to even submit an ad).
For the "ad" sites that don't charge for listings (e.g., EscortDirectory), pics veracity is like many other things on the WWW (i.e., the wild, wild, west). Many of those sites scrape info, pics from the paid sites and post ads without a providers knowledge. The other day I received email from potential client via one of those sites that I've never submitted to and when I looked at profile they had for me, the true pics were from before my FFS surgery and a few were even of somebody else. lol
Unfortunately hon, like many things in this world, it comes down to money. When your looking at ad sites that don't charge for listings, or charge you to peruse the providers, the buyer beware risk goes way up.
Warmest hugs & happy hobbying,
Kacy TGirl