A new idea for a baby shower theme is to take a children's book and make it the theme of the party. For example, "The Velveteen Rabbit" is a classic children's book that parents can build a party theme around, from the cake design to the party favors and decorations.
Another new idea is to take inspiration from a vintage video game, such as "Space Invaders" or "Super Mario." This is a useful idea regardless of the child's gender, since there is a wide variety of mainstream male and female video game characters. This idea has the added benefit of creating a sense of nostalgia for the parents if the game is a childhood favorite of theirs.
One way to honor the mother of the shower is to build a baby shower theme around the mother's career or hobby. If she is a teacher, for example, the party theme could be based on a classroom, with small chalkboards, flash-card place cards and apple-themed treats. If the mother loves "Breakfast at Tiffany's," the theme could be diamonds and blue decor with white bows. This allows the focus of the shower to be on the baby, but retains an air of sophistication for the adults in attendance.