[wvenable]

Outside of obvious facial artifacts the background was the next give away. I got it correct every time.

[Zobat]

Reflections (highlights) in the eyes being different, artifacts and so on. But that said, if I weren't looking for fakes I'd probably accept them as real enough.

[roenxi]

As soon as I started paying attention to the faces I lost my streak; they are basically perfectly realistic. But the backgrounds are a dead giveaway.

[baxtr]

Same here. Just looked at the background and got all (10/10) right.

[number6]

so next: generate green backgrounds and use the same background in both pictures