#1) Pretty cool. I like the subject, the lighting. It's a neat shot.
#2) Good lighting level in the window and curtain. Too dark in the area surrounding it. This would be a good shot to bracket. Learn how, it's easy, and worth your time. There's a good guide that's stickied in the photography section.
#3) Great subject and good lighting. Work on getting your lines straighter.
Look at the window. See how it doesn't line up to the straight lines that I drew? Especially the leftmost vertical line- the window curves in as it goes up.
Part of this is lens distortion, which usually isn't too much of a problem. It can be removed, though. A bigger factor is how you align your camera. You want your camera to basically be parallel with the ground, and perpendicular to the wall. Here is a pretty good article about it:
https://photograph...and-aligning-lines #4) I like the idea of the shot, but it looks forced, awkward, and staged. Maybe it's that the subject isn't that interesting, or that the unicorn doesn't really fit.
#5) I like it. Maybe try to get more of the subject in the shot. Try backing up a little more. Also, I would try to get the shot again, moving yourself to the left. Having the corner in the middle might look cooler, with the lines converging in the background. *Not sure how that would look, but just experiment with different angles. Pay attention to how the subject AND the background look.
#6) I'm going to agree with Ganesha on shot 6. Being in the corner would convey more motion.
Though, I will say, you did a pretty nice job of lining up your shot. All the lines are straight, they converge nice.
I think you could have more dynamics. This could be another shot to try bracketing, if you wanted. It isn't necessary, but it'd be something to try.
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Overall, nice job. You're really getting the hang of things. Don't take my advice too much to heart. Ultimately your photography is for you. These are things that I would try, but they still might not necessarily look good to you (or me).
Just play around. Flash cards are cheap. Take more pictures than you think you want or need. Try different exposures, different angles. Play with the subjects. Get creative.
You're doing a fine job. Keep at it!