3 things I look at when I evaluated pics.

1. shadows
2. edges
3. background and central figure

Shadows is the first clue if it doesn't fit. It's very hard to fake shadows or personally, I don't know how.

Edges for me is the dead giveaways. Like this pic, if I were to fake this, stick Lebron James face into another person's body so I will look at the edge of the face, or stick clothes on Lebron James's body. That will be the other way so look at the edges of clothing.

As for background, you know what I mean. If he dressed like this in the woods, you know it's fake.