What time of year were you thinking?
Here are a few ideas
Bronze Bull Ball -
You could decorate w/ all sorts of golden toned fabrics for the tables and chairs. Maybe your invitation could have a bovine hoof print on the front of a stiff card stock, in a bronze tone. You echo the same mark on the table cards. A stamp would work well.
(something like these)
You could even spray paint bronze little bulls that you can find in the cheap farm animals toys you can buy at walmart, and glue them to ribbon or napkin rings to make napkin holders.
You could decorate cookies in the shape of a bull and give them away as party favors.
Good Fortunes "Spring" Formal -
An Asian theme might be fun with chop-sticks, sushi, fortune cookies... and any other food you might like. There is really no limit to what you can do. You could get bamboo for table centers and the girls can take them home. I had a friend give me a lucky bamboo for a graduation gift and I love it.
A lot of restaurants can sell or give you the take-out Chinese food boxes that can be used to put favors in. http://store.yahoo.com/asianideas/mintakoutbox.html
It looks like you might be able to get them in green or yellow. White would work and you could add like a green or yellow ribbon.
Mad Bull Formal/ Mad Hatter Formal-
Think Alice In Wonderland. What ever you can think about from the movie can be used for decorating. You can make it really crazy with bold colors and patterns for the tables. As a fun thing… get all the girls to decorate a hat and have a contest to see who has the craziest “themed” hat.
Fishing under the Moonlight
Retro Formal- everyone dresses from a certain era. A 50’s sock hop for example lol
If I can think of something else I will post back