Korean Messaging App Has More US Users Than Path

I live in South Korea and use KakaoTalk ("Katok"). I haven't exchanged phone numbers with a Korean in the past year who didn't already have the app.

I know because the moment I add a phone number to my iPhone address book, KakaoTalk notices it and adds that user to my contact list, along with their photo.

Everybody has a KakaoTalk photo, many have 4 or 5. I haven't been able to figure out how they do that. I can only find the setting for one user pic. Perhaps they do it with the associated app, kakaostory, which is sort of like a blogging engine on top of the Kakao platform, if I understand it.