The central themes in The Pictures of Hollis Woods are the twin concepts of family and unconditional love. Hollis, who has never had a family, has an idea in her mind of what an ideal family looks like, and she treasures a representation of one she made when she was six. That picture has in it a mother, a father, a brother, and a sister, and Hollis almost achieves that perfect balance for herself when she stays with the Regans over the summer. Families are made up of unique individuals, however, who must learn to interact positively for the good of the whole in a process that is never ending and can sometimes be messy and uncomfortable. Hollis's inexperience with the dynamics of family life causes her to misinterpret the discord that occurs so frequently between Steven and the Old Man, because she doesn't "know about families yet." Hollis believes that she is the cause of the rift that she sees growing between Steven and his father. Convinced that she is "messing up the family," she sacrifices her own desires to keep from hurting the Regans more than she believes she already has.

The love that binds families together is unconditional, and it is this that Hollis cannot understand. In her experience in a long line of foster placements, when she has been "fresh," "incorrigible," and "a mountain of trouble," she has been sent away. The Regans, however, are "different" and love her even though she insists she caused the accident that almost killed Steven; they continue to prepare her room in hopes she will come to stay, even when she says repeatedly that she will not. Interestingly, Hollis knows instinctively how to give love, but she has no idea how to accept it. When she first considers taking a chance with the Regans and letting them love her, she makes sure to tell Steven all the bad things about herself; she confesses she runs away sometimes, ditches school, and has no friends because she is mean. Steven accepts what she says without condemnation, and Hollis is amazed because Steven now knows "all about me and he (doesn't) mind." Steven, unlike Hollis, has grown up in a loving family environment, so he knows how to both give and accept love. Even though, in his constant quest for independence, he insists on being contrary and always seems to receive the Old Man's ire, he understands that their conflicts are a part of normal, ever-evolving family relationships, and he is secure in the fact that the Old Man will love him no matter what.

Hollis's understanding about families develops slowly through the narrative. Although her idea of the perfect family is the classic one with a mother, a father, and a sibling, she intuitively senses that its true significance is something more. One night, Josie anticipates Christmas with childlike exuberance as they walk home from the movies in the rain. Hollis has "a strange feeling" as she stands watching the "old lady danc(ing) in the street" while everyone else her age is "home doing homework for school tomorrow." There is no doubt that her placement with Josie is unconventional and far from ideal, yet, without knowing why, Hollis wants to stay. She wonders if it is because Josie needs and truly wants her, both elements that are central to belonging in a real family. Families do take many forms, and though she will always ache for the ideal family in a classic sense, Hollis intuitively recognizes the value of the imperfect and loving relationship she has with Josie. She tells herself, "it's enough . . . more than enough."

Another important theme that is examined closely in the book is the power of art. The narrative is peopled with artists of all sorts: Josie and Beatrice are both retired art teachers. Although Josie is losing her memory, she can still capture with beauty and grace the essence of a person in her carvings. The Old Man is an artist too, although his art is of a different kind; he draws "circles and lines and squares that (turn) into plans for houses and buildings." Of course, the artist whose gift is most intricately scrutinized is Hollis, who has the uncanny ability to accurately reproduce the images that she sees and remembers. Art is a refuge for Hollis, who has found that it is the one thing she can count on when everything and everyone else is inconstant and undependable. It is also an avenue to learning; as Beatrice says, "Sometimes we learn from our own drawings . . . things are there that we thought we didn't know." It is not only physical detail that Hollis captures in her art; she somehow manages to recreate subtle nuances of interactions and feelings. In looking at the product of her art, Hollis discovers things that she missed when she was looking at the scenes in real life. Beatrice says that Hollis' art is a "language you speak on paper," and Hollis recalls that the Old Man had noted, "Look at a picture one way and you'll see one thing . . . look again and you might see something else." Art is valuable because it holds truths that are often missed by the naked eye, and Hollis learns that "you have to keep looking to see everything." With its power to communicate things "that we thought we didn't know," in Hollis' case, art is instrumental in the development of her understanding of what love really means.