Some appropriate themes to use for a baby shower to celebrate a baby boy include an "A'hoy, it's a boy!" nautical-themed shower, "king of the jungle" animal-themed shower and a "take me out to the ball game" baseball-themed shower.
Baby showers for a mother expecting a boy can have a wide variety of food and decorations to match the theme. If the host does a baseball-themed shower, the guests could be served hot dogs, popcorn and cracker jacks. A cake in the shape of a catcher's mitt, ball and bat would expand on the theme. Decorations such as baseballs and pennant flags add to the "take me out to the ball game" theme. The host could even ask the guests to dress as if they were ready to play baseball.
A scrapbook baby shower is another possibility that would work well for a boy's shower. The host provides scrapbook materials such as card stock, scissors and glue. The mom then adds pictures of the baby as he grows and reaches various milestones.
Hosts can also plan a shower based on the colors blue and green if they are looking for a simpler theme. Using different shades of blue and green for decorations and party favors lets the guests know that the party is in honor of a baby boy without much detailed work.