The most obvious thing we can start with the "grills!" They establish that Batman and the Joker have already battled, those are crowns, replacements, probably for all the teeth the Dark Knight has already knocked out. This implies that a rumor from not to long ago Amanda Waller see's the Joker as a valuable asset, due to his encounters with Batman are true.
Suicide Squad and Batman v Superman may be setting up the future for the rebooted Batman films without our knowing.
Batman in this newly established DC cinematic universe is said to be rarely seen, and that there is no photographic or video footage of him in existence, leading to believe how badass this Batman can be Affleck or not.
but enough about him.
The same can probably be said about the Joker he may be a criminal but like his opposite there is little that is known about him, and this makes him more dangerous. Whether the inspiration is drawn from Grant Morrison, Scott Snyder or Alan Moore, with Oscar caliber acting under his belt Leto has one crazy task ahead of himself but I feel he is up for it.
I loved Heath Ledgers portrayal of the Joker in more of a Realistic interpretation, but his inspiration wasn't really drawn from the comics too me, it was beautiful and original and cannot be topped, but I believe that Jared Leto will give us our most impressive look from a True-to-the-comic standpoint. His portrayal will lean more how the Joker is in the comics, and I don't mean to discredit anyone who played the role either
Both Jack Nicholson's and Cesar Romero's portrayals of the Ace of Knaves we're brilliant but took inspiration from the joker of the time. David Ayer however seems to draw heavy inspiration from the Joker of the Morrison and Snyder era, Alan Moore's inspiration draws from the relationship Batman and the Joker have.
In Suicide Squad Joker is said to be in Belle Reeve in a straight jacket before being free's he is there mainly to keep Harley Quinn in check, but these are just rumors except for the grill thing that will be true I even tweeted Ayer himself to see if he could confirm it for fans
Any who this is all until confirmed speculation, but if we put out Ideas and get our opinions heard, these directors who take these characters we love and bring them to life, they listen Thank you DC
FYI I would recommend reading the entirety of Grant Morrison and Scott Snyder's respective runs on Batman.
Here's to you David Ayer.
and Happy Birthday Mr. J