It looks pretty good as it is, unfussy and definitely not girlie so that a guy would be happy with it. Having three sons of my own I'd hazard a guess they wouldn't want flowers or vines, they'd think that was girlie. If the intended recipient has any keen interests - sports, cars, favourite football time, music etc would it be possible to appliqué appropriate motifs etc onto the white? Other than obvious masculine stuff I'd leave it and just focus on the quilting.