Combine the Italian seasoning, onion powder, garlic powder, cumin, smoked paprika, salt and pepper in a small bowl. Toss the shrimp in the seasoning in a large plastic bag. Set aside.
Chop your tomatoes, green onions, avocado, and limes for garnishes and set aside.
Heat two tablespoons of olive oil in a large skillet heated to medium high heat. Cook shrimp 3 minutes, flip, then cook 2 more minutes or until shrimp is pink and tender.
Heat the refried beans in a small sauce pan on the stove or microwave them until warm.
Assemble by covering each tostada with a spoonful of warm refried beans, cooked shrimp, and the rest of your fixings.
If you would like to make homemade tostadas just heat a large skillet over medium heat with just enough oil to lightly cover the bottom of the pan. Heat 2 or 3 corn tortillas for approximately 3 minutes on each side until golden and crisp. Lightly salt them if you wish.
Making the tostadas instead of using the store bought version makes this a bit longer than a 15 minute meal to prepare, but it is worth the extra effort!