I must say, I've never been a fan of copying other people's art, especially when it comes to public display (which, of course, would be considered theft). At times, it's better to look around at pictures and such to get inspiration, rather than directly copying. Art is about expression and technique. You can't express yourself though copying other drawings and it's hard to show your 'improvement' if all you've done is copy, copy, copy. I myself never copy. I never needed it to improve my art. Some observe certain techniques in the drawings and paintings of others and develop their style form it- which I don't think is a bad idea. Fanart is also alright, I've drawn fanart myself; however, I dislike when people copy the style of the original art. Fan art is a show of appreciation of certain characters, etc. in your own style. If I created a comic or such, I'd be amazing to see fanart that appears in all sorts of styles and settings, rather than just a copy of something I might have originally drawn. Either way, to be blunt, it just doesn't look as good if you copy. Your personal style comes from personal expression. The art you copy may not have a fitting style for you. Only you, drawing on your own, can discover that.