This Doc Brown guy sure does love clocks. However, we don't think the director threw all those in here just to indicate that their owner was fascinated by hand-crafted, antique timepieces.
Hopefully this one jumped out at you. The entire movie is about time so the wall of clocks on clocks on clocks are clearly symbolic of Doc's obsession with time, as well as of time being a focal point of the entire film.
The very first sound we hear is a ticking clock, and the very first thing we see is a clock. Directors spend a lot of time laboring over what that initial image is going to be, so you had better believe it isn't there by accident. Ninety-nine times out of a hundred, it means something.
And this isn't that one time out of a hundred where the director simply threw something up on screen and decided to call it a day: both time travel and the idea of timing are uber-important in Back to the Future.
There's a little ditty from 1960 (that college-aged Lorraine and George probably danced to) called "Good Timin.'"
The chorus states, in true cheesy doo-wop style, "Oh you need timin'/ A tick, a tick, a tick, good timin'/A tock, a tock, a tock, a tock/ Timin' is the thing, it's true/ Good timing brought me to you."
It ain't poetry, but it gets a point across (with bonus clock sounds!): timing is key in love. Marty screws with the timing of romance when he pushes George out of the way of Lorraine's father's car; timing is crucial when George is set to punch Marty in order to save Lorraine; the kiss Lorraine and George share at the Most Important High School Dance Ever is directly related to ensuring their baby-making sessions down the line.
And lets not forget that timing is crucial for Marty getting back to the future—he literally has to catch a lightning bolt, which are kind of notoriously fast things to catch.