I love, love, love that layout!! Couple of suggestions, if you like lights, make sure you hang a lot of them from the tree. Or, hang lots of "stuff" (ghosts, bats, spiders, skels, etc.) in the tree and use spots to emphasize. If you have a projector, you've got the perfect screen under the eaves in the front to show movies. I like the silent horror films and the TOTers do too! A cemetery on the front lawn would be great. Especially if you have or can make a pop-up or breathing grave. Or, I've seen some gorgeous yards with corn shaucks and lights. Very dramatic.
For the carport, how about a séance scene? You can hang some colorful sheets around to enclose the sides and set up a crystal ball or yard globe and tell fortunes. Or, if you have a skeleton or other body hanging around, you can set the scene using her. Colorful hippie-looking clothes and a long curly wig with a turban will do the trick.
Whatever you decide, please post pics!