Eagle-eyed viewer eobardthawne42 spotted a fantastic Harley Quinn easter egg in the newest Suicide Squad trailer.
Upon repeated viewings, a familiar costume can be seen behind the black case to right. The costume in question is, of course, the classic red and black jester outfit that she's most synonymous with in the comics, and Margot Robbie did recently confirm they tried several outfits on for the film, including that one.
You can see it much clearer in the closeup shot above.
There were many that were disappointed the classic suit wasn't used in the film, though never say never. She just might end up in the costume at some point down the line.