Some good themes for a Baby Boy baby shower could be easy with just blue or more creative with things like rubber Duckies,Monkeys,Prince crowns, and so on. http://www.partypail.com/boy-baby-shower-themes.html
Examples of themes include Winter or Summer (depending when the baby is born or due!) garden-themed, eco-friendly or the good-old-fashioned boy or girl themed shower.
Following are some fun ideas for a baby shower: Stork delivery theme, nursery rhyme theme, a Velveteen Rabbit theme or The Very Hungry Caterpillar theme. Just be sure to have lots of color and fun foods.
http://www.babyshower101.com/baby_shower_themes.html explores and gives you plenty of ideas of baby shower themes that you are seeking for. Once you go through them all, you can also explore other aspects of that site as it very useful since it is specifically everything baby-shower-related.
There are many different baby shower themes. I think the most popular is probably the stork. Noah's ark is also a popular theme. There are monkey themes, bear themes, all different type of animals. They also usually have both in either pink, blue or yellow depending on the sex of the baby.
Some examples of good baby shower favors are personalized napkins, customized candies, and candles.
There are many different messages for baby shower invitations. Messages like, "Please attend my baby shower!" or "Hope you can make it!" are good messages.
Some baby shower theme ideas include animal themes. These can include: butterflies, ladybugs, safaries, monkey, etc. Noah's Ark is a cute idea as well.
Some ideas for baby shower parties are animal themes, such as a jungle theme, or a Noah's Ark theme. You could also so turtles, elephants, monkeys, or giraffes.
I would think most games would be gender neutral at a baby shower... but you could decorate onsies with boy themes (trucks, airplanes, dinosaurs). Here is a website with some baby shower games! http://www.babyshower101.com/baby_shower_games.html
Any type of baby shower favors are good for a twin baby shower as well. Chocolates, little photo frames etc. You can find some ideas here: http://www.prettybabygifts.com/baby-shower-favors.html
Some ideas for a boy's baby shower would be themes such as cowboy, trains, circus, baseball, football or any other sport. You can buy decorations and paper goods that relate to the theme you choose.
A centerpiece with a picture of a Baby boy on it or a Baby girl is a really good idea for a baby shower centerpieces. Also a picture of a diaper and a binkie might be good.