Sometimes when people cum they look unattractive. You can do cute twitches or make a crinkled monster face. That being said, I don't think worrying about it is important. A British artist has taken photos of the faces of men cumming and will display them in a popular cruising area of Los Angeles.
Boyfriend 1: Were you outside blowing someone last Saturday?
Boyfriend 2: No, but I saw your face hanging from a tree. It'll be your neck if I don't join in.