Mother Goose nursery rhymes are a classic starting point. There are numerous nursery rhymes here that can provide a theme for your baby shower or you could choose to incorporate touches from the more popular nursery rhymes in the baby shower.
There are downloadable nursery rhyme cards that are used for educational purposes available all over the web. Simply printing your invitation at the back of these cards create an inexpensive and unique invitation that announces the theme of the baby shower very clearly.
You can easily make your party area a veritable nursery rhyme wonderland. As a base, nursery rhyme books can be used as stands to display little vignettes scattered around the room. What's important to remember is to mass the decorations together to create a bigger impact than putting objects around piecemeal. For example, in a corner of the room already decorated with a potted plant, add a small stool covered in green fabric to represent a tuffet, top it with a cereal bowl filled with white flowers and add a spoon for extra effect. Remember to suspend a spider from one of the plants with black thread!
Another table can hold a toy horn tied with a blue ribbon, or the food table can be lorded over by a giant styrofoam egg that's been painted to look like Humpty Dumpty. You could also paint a mural on a large piece of paper with a scene from the land of nursery rhymes.
If you can find a large plush goose or a goose lawn ornament, outfitting it with a baby's hat or bonnet makes Mother Goose. Put your floral centerpiece in Jack and Jill's bucket and have Jack be Nimble's candles at the table, too. Plush sheep can also be used in varying arrangements so Little Bo-peep can have fun searching for them!
Of course you won't serve curds and whey, but the Queen of Heart's Tarts, Polly's tea, Jack Horner's pie, or the Muffin Man's muffins give you a starting point. For a cake, you could make one “marked with a B” or have one inspired by a nursery rhyme character like Peter Piper (a pumpkin-shaped cake) or the classic Humpty Dumpty.
A pictionary or trivia game based on nursery rhyme characters or a game of charades where the guests have to guess the titles of the nursery rhymes will test how much they remember of the stories of their childhood. You could also play a version of the memory matching game where each guest has to match the beginning and ending of a nursery rhyme.
The perfect favors for the nursery rhyme baby shower could be little
plastic eggs filled with candies. Or, to echo another nursery rhyme,
give a lily flower bulb so they can answer the question of, “How
does your garden grow?”