1. I really like this picture, very nice composition and pleasing DOF.
2. The flower looks overexposed.
3. The subject is too small. Either a tighter crop or a lens with a longer focal length would have been better. Also, the grey-ish background isn't very pleasing.
4&5. Again, the subject is too small. Furthermore, putting the subject in the very centre of the image usually doesn't create much tension. Take a look here:
Rule of Thirds
6. I like the idea and composition, but the small green leaves aren't that interesting to look at, I'm afraid.