Hey! =] We have a lot of similarities~ (Sorry, this answer is insanely long. ^^;;; I hope you read it all!)
I'm also a 15 year old girl, 5'7" (or 5'8", haven't checked in a while), 130 pounds, and a nerd (one AP class, the rest gifted/honors... if you want to measure it that way) who dealt with depression (very mild), and needs more confidence. I kid you not. I'm not just an adult trying to make you feel better (but would one go through all this effort?) :P I even have dark hair (though mine is darker).
I have to say though, we have different body types. I... am a stick. Judging from your photos, you have more curves than I do. But eh, what can you do. It's all about what you value. Which is a great segue to the point of my whole answer! (I better go quick or I'll ramble and this'll be suuper long).
First, what do you consider attractive? I hesitate to write this answer, because I know it will be somewhat hypocritical. Everyone has their own view of what is attractive, and though there is a large consensus among current pop culture, people do vary quite a lot... and those who will judge you just like that probably aren't worth making the effort for anyway (you want someone interesting and original, yes?). I know we've heard this a bagillion times, but I've finally started to realize that it's not important to please everyone around you, and worry how you look. So just figure out what YOU think is attractive, how YOU think you would like to present yourself, and do that! I guarantee, someone will like you for yourself. Someone will appreciate your honesty to yourself, and you will be more confident for it. (It's hypocritical of me to say this because even I still make judgements about people based off of their looks. =/ ) And yes, I do have a boyfriend (of 2 months- ish) =]
If you are confident and like yourself (not saying you don't), this will be hugely appealing to not just guys, but everyone (just don't be arrogant :P), regardless of how your hair is styled, what clothes your wearing or any other ways you could affect your appearance. Ever meet someone who just drew people to them, because they were comfortable with themselves and charismatic?
The honest truth is, you already seem to do all the things a girl should do in terms of take care of herself... i.e. the necessities, bla bla bla. You seem to wear decent clothing, you wash your hair, etc. At the very least you're not a slob. So you could try wearing more makeup, or styling your hair differently, or wearing interesting clothing to be more "pretty" but then you're just trying to appeal to those who would judge you shallowly.
Work on you, and that'll make you the most attractive.
Also, don't be in a huge hurry to find a guy. This is perhaps the most hypocritical thing I can say, since I have a boyfriend, and I really wanted one before I began to date him... but searching for "that guy" made me realize that people at this age are shallow. We judge. We're teens. That's what we do. We judge and angst about being judged. So you might not find that perfect person at your school, or just yet. Which is fine. Yes you'll have to wait longer, but it'll be more worth it. Or you could settle for less? Your call.