[notum]

Eyes and backgrounds. Easy peasy, 10/10.

Backgrounds should be generated by a different model and face should be pasted in, now that would be a real challenge! Models that fix eyes already exist.

[itslennysfault]

Or just use real background images and composite an AI face on top. The question which face is real so using the background is kinda "cheating" imo. So using a real photo for the background eliminates that technique to cheat.

[Strom]

I also got 10/10, but by looking at ears and facial hair. There's a long way to go for a test like this. That said, if I didn't know I was looking for artifacts, all of those pictures would be passable at a glance.

[lqet]

There are almost always these strangely colored, flare-like artifacts in the background or on the skin. Looking for those, I also easily scored 10/10.

[fh973]

Ears and teeth artifacts, if present.

If the head is rotated slightly, the faces, especially the cheeks are getting slightly distorted in the artificial images.