MORGAN CITY — The Louisiana Shrimp and Petroleum Festival is returning to Morgan City for its 91st year in September, and a local artist just unveiled the poster for this year's festival. On Tuesday at the Atchafalaya Intracoastal Waterway Shrimp Boil, Genevieve Breckoff-Bullock unveiled her design, which highlights the Labor Day weekend festival celebrating both the shrimping and petrochemical industries. Breckoff-Bullock, an LSU graduate livin…