Assign each child a country for which they can get props or costumes from home. Ask each child to wear a costume from the assigned country on a specific day.
Take a picture of each child in costume. Print the pictures and staple them to folded pieces of construction paper to make passports.
Study a different country each month. Watch movies about this country, play some of its games and learn a few words in its language.
Celebrate other countries' cultural holidays, such as Cinco de Mayo or Chinese New Year. Bring in traditional food and decorations for the party.