Bnai Mitzvah ideas?!? (Bat/Bar)?

I am having a bat mitzvah with my brother, we're twins, in October, but my mom said I couldn't do a Halloween because it not "Jewish". Me and my brother disagree a lot, so it must be good! I like winter, water, animals, light colors, mythical stuff like gods and goddesses, video games, music, tv, nature, stories, traveling, different languages and places(My name is Sally, it could be used in a idea). My brother, Ben, likes guns, videogames, animals, explosives, cars, skateboarding, snowboarding, tv, sports, water, fire, destruction, army, and other odd boy stuff. Please help me! I need an idea! My bnai is soon!!