These photos play several important roles in the film, both in plot and hitting emotional beats. The script does mention these photos, “He’s looking away from us, at the picture of the children on her desk” and it would normally be the graphic designer’s job to make these family photos or commission the stills photographer to take them. However, as I stated before, it must have been someone else in the art department who made these for Die Hard.
We first see the photos on Holly’s desk at the beginning of the film when she speaks to her daughter on the phone. The slow pan across pics of her children to the main family portrait shows Holly, her children and the man we’ve just seen arrive at the airport. This instantly tells us they are a family using no dialogue. After the conversation, Holly slams the photo face down, hiding her husband from view, showing her frustration and how they are growing emotionally distant.