Arrange oven racks in upper and lower thirds of oven. Preheat oven to 375°F.
Brush two large cookie sheets with oil. Whisk 1/4 cup oil with chili powder, paprika, cumin, cayenne and salt. Cut corn tortillas into 24 ghost shapes. Use a wooden skewer to punch eye holes into each ghost. Brush one side of each ghost with oil and spice mixture. Place ghosts, dry side down, in single layer on the prepared baking sheets.
Bake, switching position of pans halfway through, until ghosts have curled into lively shapes and become golden and crisp, 12 to 14 minutes. Season with additional salt, if desired; let cool completely on pans. Repeat with remaining tortillas. (Ghosts can be made up to 3 days ahead; store in a tightly covered tin.)