ORLANDO, Fla. — SeaWorld built its brand on a leaping and splashing killer whale named Shamu. She was part of its logo, gave her name to stadiums in the theme parks and was the inspiration for rides. The orca image sold T-shirts and soft, stuffed animals. With the company phasing out its orca program, it is forced to ponder the question: What is SeaWorld without Shamu? “The orcas were their most powerful engagement tool,” said Allen Adamson, a marketing and branding expert based in New York.