What ambiguous symbolism? A circular painting that they've already admitted was a mistake? A mural painted in the psyche ward, which happens to match a painting of Marty's daughter? Knowing what we know now, it was also likely another prop mistake. Lastly, a scene of Hart, where people have slowed things down, looked at it frame by frame, and are trying to make mountains out of molehills, in what is likely just a continuity error? Yeah, this show is just rife with "WHAT DOES IT ALL MEAN!?!".
EDIT: Soygen got the link first.