Preheat oven to 350 degrees. Saute celery, bell pepper and onion in butter until onions are transparent. Boil shrimp for 4 minutes and drain. Combine all ingredients in a large bowl. Add 1/2 cup shredded Cheddar cheese. Pour mixture in casserole dish and top with cracker crumbs and remainder of Cheddar cheese. Lightly drizzle with melted butter. Bake for 30 minutes.