EAST ST. LOUIS, Ill. — As a child, Mykael Ash enjoyed picking up seashells near the Mississippi Gulf Coast. His grandfather lives there, so trips to the beach were a regular part of life. “It’s peaceful energy,” Ash said. “Especially when you put that seashell to your ear.” At age 32, he still collects shells. But the terrain is different in this city of 18,000 people. Ash walks on concrete instead of sand, picking up shells left by bullets as he walks through the city for exercise. “It just hit me one day,” he said: He could use the shell casings in his artwork. Gun violence has been a persis…