the fire escape is a separator....... it separates the real things from those that are make believe
the father's picture symbolizes better days, but it also symbolizes the ultimate escape
the alarm clock signifies routine
the yearbook helps develop the theme that there are no gentlemen callers........ I don't see this as extremely important, but it does clarify that there was a time Laura was interested in finding a boyfriend, and even more so that she's lost touch with those she went to school with. I see this a proof of her isolation (self-imposed).
The unicorn signifies Laura's differences. She's a bit peculiar..... like the unicorn.
The candles signify the loss of hope; she snuffs out the candles in the way her hopes about Jim (or any man) have been snuffed out.