You can't choose a subtype, such as creature types like Spider or Hero, artifact types like Treasure or Food, or enchantment types like Aura.

Card types other than creature include artifact, battle, enchantment, instant, kindred, planeswalker, and sorcery. Technically, you could also choose land, but lands are never cast, so doing so would have no effect. (The same is true for card types that don't appear in most games, like plane or scheme.)