Famous for illustrating the acclaimed children's books Jack and the Wonder Beans (1977) and If There Were Dreams to Sell (1984), she is also well known for her work on writer Jean Fritz's Newbery Honor-winning autobiographical work Homesick: My Own Story.
Before beginning her career by illustrating Daphne du Maurier's 1959 work The Breaking Point, Tomes worked as an interior designer.
Over the course of her career, she illustrated some five dozen works of children's literature.
She grew up in Nassau County, New York. Born into an artistic family, she was a cousin of both Newbery Award-winning children's book illustrator William Pene du Bois and painter and art critic Guy Pene du Bois.
She and Robert Lawson were both New York-born illustrators.