Honestly, I think of everyone who is stealing and using a photo from another person as avatar as fraud and scammer who should be banned. Some time ago, there was a troll who stole name and picture from a German member and opened several accounts with their picture. Then there are the scammers who use pictures of American soldiers and doctors to lure their prey. And then there are those people who use pictures of celebrities who might be only known locally and not to a wider international audience, so other users might not immediately recognise that it's a picture of a celebrity, like a Turkish singer or an Indian actor. I remember, that a scammer once used a picture of veterinarian Dr. Evan Antin for his italki profile: https://www.buzzfeed.com/juliareinstein/honestly-this-vet-is-just-ridiculously-hot. Those who use the pictures of celebrities also often pretend to be native English speakers, while their level of English is clearly not advanced. But many learners here might not realise that the handsome native English speaker who is so eager to get to know them is a fraud until it's too late.

(I know that there's a grey area and some people might either believe to be native speakers when they're not or they can suffer from dyslexia, speech impediments or be deaf, so that the way they express themselves doesn't sound native, even though, they are native English speakers. But I still think that the majority of "not sounding like native English speakers" are indeed not native English speakers and know it but decide for displaying English as native English to have better chances to attract language partners or students.)