Cartoons and Movies
Cartoons and children's movies are always a big hit. Youngsters can dress up as characters from their favorite films, or you can coordinate a party where everyone comes as a different actor, setting up an entire cast of a movie. Try Harry Potter, Lilo and Stitch, Jimmy Neutron, Indiana Jones, SpongeBob SquarePants, Teenage Ninja Turtles, and Batman are all theme ideas from contemporary and classic movies and cartoons meant for a young audience.
Chronological Theme
Choose a decade or clothing theme in American history. Themed adult parties and get-togethers often call for fashions of the 1960s or 1970s, but that doesn't mean kids can't dress up in bell-bottoms, flowery dresses and funny wigs to impersonate the same characters. Other well-known clothing styles throughout history include Western, 1920s, 1950s, 1980s, space age, Victorian, grunge, disco and the Stone Age.
Favorite Activity
A child's favorite activity could constitute as a theme for a party. It could be a sport, a game, a holiday or a craft that employs a certain type of dress. A cheerleading party for those who like to cheer, bowling, football, soccer and baseball are all great theme ideas. A chef party where little chefs can convene, a tea party, gymnastics and a magician party are examples of children's themes. Additional activities that could be employed as themes include dance, musical instrument playing, board games, video games, and painting and drawing.
Different Lands
Parties can be location themed to evoke the feeling of going away somewhere on vacation or just going on an exciting field trip. Travel ideas like going on an African safari or an around-the-world sailing adventure are themes that are easy to orchestrate with a few props. Pretend everyone is traveling to France, camping in the woods (you can actually set up tents in the backyard), hanging out in Hollywood or wading in the desert past the pyramids.
Archetypal Characters
You can also choose an archetypal character all children know about like a fairy, a pirate, princess/prince, cowboy/cowgirl, angel or devil to lead the theme of the party. There is always the possibility of combining themes like angel and devil.