Stir together lime juice, salt, and jalapeño (if using) together in a large bowl and add shrimp. Toss shrimp to coat completely in lime juice. Cover bowl and place in fridge for about 30 minutes. Check shrimp and if they're turning pink, remove from lime juice; otherwise continue to marinate for 15 more minutes.**
Put rice, water, and salt in a medium saucepan and bring to a boil. Once boiling, reduce heat to low, cover saucepan and let cook for about 20 minutes, until water is absorbed and rice is tender. Turn heat off and keeping saucepan covered, let rest for 10 minutes.
Transfer cooked rice to a large bowl and toss with seasoned rice vinegar. Let cool to room temperature.
Divide cooled rice into 4 large serving bowls. Sprinkle a little furikake over each. Equally divide shrimp, sliced avocado, chopped mango, chopped cucumber, shredded carrots, and edamame over the rice in each bowl.
Drizzle sriracha mayo over the top and sprinkle with more furikake if desired. See post body for more ingredient add-ins and topping options you can use.