Answer: The gravestones of all of his brothers.
Step-by-step explanation:
In Great Expectations, by Charles Dickens, the “five little stone lozenges” refers to the gravestones of Pip´s dead brothers. Pip explains that he imagines how his brothers looked like solely based on their gravestones. It´s the same he did with his parents, who are also dead and buried in the same graveyard.