"Apple knows whats good for you, so you're gonna' like it"- i read it somewhere here in this forum, and it fits here. Right now you can't disable the contact poster feature (if thats what you are referring too). Its not a solution, but maybe it helps:
What i did is, i put an "unknwon user" picture i found via Google to all Contacts.
Also i edited my contacts online (using Google Contacts, i did not edit them right on my phone). The picture shows up correctly in the contact details. And if someone calls, having contact posters available, it doesnt show up anymore.
Nowadays, the contact with the unknown user picture shows up again, anyway when i hang up i quickly see the contact poster for a split second. So i assume the poster is there but its overwritten.
If you've configured your own contact poster for a user, i figured i need to dlete the whole contact, re-sync and then can start from fresh. Or I simply put another picture into the contact like explained above. Honetsly, i think this feature is currently just buggy, there is no real explaination how it behaves.
Anyway, i hope they allow users to opt out of this contact poster stuff.