While I was surfing through collections of his work via the Internet, I came across three unfinished works. I'm not sure how interesting this is for the average reader, but I know that people who paint, along with art historians, usually enjoy stumbling across such items that reveal an artist's technique.
One of Pissarro's earliest surviving works. Painted on his return to Saint Thomas, but quite possibly interrupted when he left again for France. At this stage of his career, Pissarro seems to be finishing a painting area-by-area.
Thirty years later, he is more into assembling his painting on a balanced basis. This seems to be a gouache or watercolor that requires different handling than oils. Nevertheless, he leaves important areas to be finished later.
Here Pissarro spent his time on the featured foreground subjects. Heads and faces in the distant crowd might or might not receive a bit more detail. The far side of the market square is was roughed in when he set this painting aside. (Though he did add his initials instead of his usual signature, indicating ... something.)