Large framed photographs of healed hands have been hung to offer the major hope.
The major's injuries are not only physical ones, they are also deeply emotional. The fact that the major does not look at the portraits of the healed hands suggests that his emotional injury is more damaging than his physical injury.
The unexpected loss of his young wife leads the major to angrily tell the narrator never to become attached to something that can be lost. This loss of composure in the major is a shock to the narrator, who sees the major as a man of great restraint and dignity. He is overwhelmed, however, by the loss of his wife, saying, "I cannot resign myself."
If the major truly cannot resign himself to the loss of his wife, he will never be healed. The photos of healthy hands then stand as a contrast to the permanent emotional injury he has sustained in losing his wife.
No rehabilitation machine can possibly help him cope with his emotional loss.