Preheat oven to 450 degrees.
In a glass measuring cup or small bowl combine the oregano, thyme, basil, cayenne, creole seasoning, cajun seasoning, pepper and salt. Whisk to combine. Working with four tortillas at a time, microwave them for 1-2 minutes. Quickly rub with olive oil and sprinkle one side with the spice mixture. Just do a sprinkle, about 1/2 teaspoon to 3/4 teaspoon, on each tortilla reserving the rest of the spice mixture for later. Place tortillas on a taco mold if you have one. If not, invert a regular-sized muffin tin. Fold the tortillas gently and prop up between the bottom of 4 muffin cups. Bake at 450ºF for 5-7 minutes or until crisp and lightly browned. Repeat with remaining tortillas.
Heat oil in heavy large skillet over medium high heat. Add onion and saute for 7-10 minutes, add garlic and sauté until fragrant, about 1 minute. Add shrimp and about 1 1/2 tablespoons of the spice mix. Sauté until just beginning to turn opaque in center, about 4 minutes. Transfer to a small bowl.
To the same skillet add the bell pepper and saute about 5 minutes until slightly soft, but still crisp. Add the tomatoes and simmer for 3 to 5 minutes and then add then add the shrimp back and toss well. Simmer one more minute and then remove from heat. Taste and add a teaspoon or so more of the spice mixture if desired.
Fill the taco shells with the shrimp and peppers and top with cheddar cheese and avocado if desired.