The first and most striking thing worth noting about Leto's Joker is the ink covering his body. Rumors suggested that Ayer's take on the Clown Prince of Crime would be heavily tattooed for Suicide Squad, but few could have predicted just what that would look like.
As unconventional as they may seem, tattoos on the Joker are nothing new. Frank Miller and Jim Lee delivered a tattooed Mr. J in All Star Batman & Robin, though there he sported a dragon tattoo on his back as a nod to Red Dragon's Francis Dolarhyde.
Here, Leto is sporting tattoos that strike up some familiar Joker iconography; the laughter across his chest and arms, the giant grin on his forearm, the deck of cards with the words "All In," the skull and jester's cap (reminiscent of the Joker cards he leaves at crime scenes) and of course, the "Damaged" tattoo on his forehead, which is a tad on-the-nose. He even has what looks like a dead bird on his bicep... a nod to a dead Jason Todd/Robin, perhaps?
Now, the question is, are the Joker's tattoos merely body art, or a sign that he's spent some time in the criminal underworld? Time will tell...