I just did a king for my seventeen year old son. His directions to me were "I don't want any girl fabric or girl pattern. It took him a year to decide on fabrci and the pattern he liked was 20" blocks cut in half and resewn with different halves. I used five coordinating fabrics (blues and golds) . One paisley, others small geometrics. I must admit it was georgeous. chose a very ornate but masculine quilt pattern. He loved it.
Bottom line: let them choose.