Look at the white block on the far right side about one-third of the way down.

edit: And the white block on the top, far right a little in. <3

And just right of the left hand side black border, about halfway down.

And the white block to the left of the F on the bottom right serial.

And the white block in the top of his hair.

The "About" page shows a few choice selected ones at the bottom. I like the artist who expresses an opinion of the payout rate for the task set before them!