Place the shrimp in a large mixing bowl, then sprinkle with chili powder, cumin, paprika, and salt and pepper. Toss to coat.
Heat olive oil in a skillet over medium high heat and cook, stirring occasionally, for 2 to 3 minutes or until shrimp are pink and opaque.
In a small bowl, combine avocado, diced tomatoes, shallots, cilantro, and lime juice. Season with salt and pepper to taste.
To assemble, place crackers on a serving platter. Spoon approximately half tablespoon of avocado salsa onto each cracker and place a shrimp on top. Serve immediately.