To be sure, any criticism/advice that I can offer is nothing compared to the advice that professionals like
iGary can give you...I'm only 17 too, and I'm still learning...A LOT
Anyway, the first page of the site is very, very neat - although I would make it so that there is no scrolling available (i.e. cut it off vertically). My sister visited the site as well, and couldn't figure out how to enter it (I know, I know - you just click on the logo - but shortening the page might make this more clear).
Once I entered, though, there wasn't much there to critique. There's nothing in the main window, until you scroll rightward. Horizontal scrolling is very cool, but again, my sister didn't know where the pictures were, so consider adding an arrow at the top of the screen to show viewers that they can scroll rightward.
You're going to need to add some more pictures for anyone to really give you some solid advice. To be honest, while some of the pictures were neat (i.e. the girl holding the chain), others were less unique. The picture of the sunset, for example, had too much sky - the picture of the yellow flower (and weeds) could use some cropping, and its very difficult to take good macro pictures of flowers at night. The picture of the plant on the beach looked cool in its thumbnail, but looked worse when blown up, proving that good cropping does make a difference.
Like I said, I'm still learning - but this is a great site to come on to look for advice. I know everyone else here has helped me out a lot so far...hopefully they'll do the same for you

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By the way, to look at some comparable shots and a website by another 17-year-old, visit my site (and even more specifically, the 'nature' portfolio):
http://web.mac.com/c.peters06/iWeb/Site/