The error is "everyone". It should be "every one".
"Everyone" means "all people", which does not apply here since the speaker is talking about the paintings. In this case he means "each painting".
Note the difference here:
Everyone deserves a medal. (all of you)
Every one of you deserves a medal. (each of you)
Both of these have the same meaning but the details are different. The first "all" is collective, while the second "each" is individual, which changes the nuance.
Everyone is going to the game.
Every one of us is going to the game.
The second sentence emphasizes that, individually, we each chose to go to the game. The first sentence is more a simple statement of who is going.