Place the shrimp and lime juice into a large bowl, and stir to coat. Let stand for about 5 minutes, or until shrimp are opaque. The lime juice will cook them. Mix in the tomatoes, onion, and cilantro until coated with lime juice; cover and refrigerate for 1 hour.
Remove from the refrigerator, and mix in the Worcestershire sauce, ketchup, hot sauce, salt and pepper. You can leave the hot sauce out and let people add their own when serving if that is preferred.
Serve in glass tumblers and top with avocado pieces and green onion. Set out extra Worcestershire sauce, ketchup, lime wedges and hot sauce for people to individualize their dish. Serve with whole grain crackers.