It takes more than Band-Aids with cartoon characters to put children receiving cancer treatment at ease, but Leo Flores knows how.

A post-anesthesia care unit nurse at MD Anderson Proton Therapy Center, he makes a point of getting to know his pediatric patients, who may undergo a series of 30 treatments in six weeks.  It doesn’t take too many visits for the self-taught artist to figure out what to paint for them over the course...