Roughly chop the shrimp. Pour the black bean salsa on top of the shrimp, cover, & refrigerate for an hour. Chop the tomatoes & cilantro. Combine in a bowl. Cover, & refrigerate until you want to serve. Prep the taco shells with shredded lettuce. Dump the shrimp/salsa mixture into a skillet, & cook on medium heat for about 5 minutes - just to warm through. Using a slotted spoon, divide the mixture among the taco shells. Top with tomatoes & cilantro.