Pre-heat oven to 400 degrees and line a baking sheet with foil. Brush tortillas evenly on both sides with half of the olive oil (1 tablespoon) and 1/2 teaspoon of the salt. Bake for 4-5 minutes per side or until brown and crispy.
While the tortillas are baking, heat the remaining olive oil (1 tablespoon) in a large skillet over medium-high heat. Sprinkle shrimp evenly with remaining salt (1 teaspoon), cumin, garlic powder, smoked paprika and cayenne. Sauté until shrimp become orange and cooked through, about 3-4 minutes; remove from heat.
Begin assembling tostadas by spreading each tortilla with two tablespoons guacamole. Top with 6 shrimp and optional garnishes (i.e. shredded cabbage, cilantro, etc.) Serve immediately.