Marty has a bigger print of the picture of him and his siblings taped above his bed.
The alarm clock that Doc uses to tell Marty when to start driving toward the clock tower in 1955, is still on the dashboard when Doc picks up Marty and Jennifer.
Have seen this movie at least 30 times and just noticed the bigger print of the picture above his bed when I watched it again yesterday, nice catch!
Also finally understood Docs reference to the photo when he says something like "photographic fakery...you cut off your brother's hair." Never got that until yesterday when I realized that Dave's hair/head was already beginning to disappear.
So many details, so many details!