As a fellow artist the best tip I can really give you is to look at professionals and inspiring artists who do photography. Hell! Even look at painters and all other sorts of artists. You are really talented for your age, but like most artists you can stand for improvement [you already know this since you're asking and what not.]
But like I said, looking at other artists is not only inspiring but it helps you learn things about composition, lighting, themes, symbolism, as well as many other things. As artists we are constantly changing and growing throughout our lives and our tastes change too. Just keep an eye on your peers and when you do look at their work try and pick it apart. Determine what you do like about it and what you don't, what you think could be better. Critique is one of the best thing an artist could ask for, maybe finding a buddy to critique with could also help.
Also, never be afraid to explore! Try using different camera's and techniques [film, polaroid, old 35mm's, expired film, double exposure.]
And just so you don't think I'm an over critical jerk who doesn't know what they're talking about, here is my site,
cwolfe.carbonmade.com