01 -  In a bowl, toss the shrimp with olive oil, chili powder, cumin, garlic powder, salt, and pepper. 
 02 -  Heat a skillet or grill pan over medium heat. Cook the shrimp for 2-3 minutes per side until pink and cooked through. Remove from heat. 
 03 -  In a separate bowl, mash the avocados. Mix in lime juice, cilantro, jalapeño (if using), and a pinch of salt. 
 04 -  Spread a generous layer of the avocado mixture onto each tostada shell. Top with grilled shrimp. 
 05 -  Garnish with extra cilantro and serve immediately with lime wedges on the side.