I would agree that your ISO appears to be too high, because there is a lot of noise, although this could also have been introduced in editing. Keep in mind, reducing the file sizes for the web has the side effect of hiding a LOT of the noise. If we can still see the noise at all at web resolution, then it's going to almost unusable for any kind of print media.
#1. The lines created by the contrete wall are nice, but then there's all these other lines and other distracting elements that clutter it up. Also, trees in the background are overexposed.
#2. Underexposed. Of course, this arguably could be deliberate, but it looks accidental to me.
#3. Probably my favorite in the set. It would look better if it had more perspective though. The two lines from the two things hanging down are perfectly parallel, indicating the subject of the picture is far away, which makes the viewer feel detached. I love all the texture in the concrete though.
#4. You never want to light a picture with one pure color, especially from an LED. It confuses the hell of the sensor and leads to an incredibly narrow dynamic range, giving pictures this extremely high contrast look. A hint of white light or some other color from a different angle could have made this picture dramatically better.
#5. This one is cool! Underexposed around the edges, but that's not necessarily bad in this case - it looks deliberate. Nice composition. Subject is a little cliche. (But then, what exploring photo ISN'T cliche?)
#6. So much potential, but the noise is killing it. It's especially visible in the black areas at the top. Also, I wish the white area at the bottom was either
completely blown out, or completely visible. The random lines through the pure white areas take away from it.
#7. Good DOF work! Love it!
Sorry, hope none of that was too harsh! You're off to a good start here, keep playing around!