I'm going to comment on each one- my opinions are free, so take them for what they are worth
1) I like the verticals in this shot, but the fence rail in the background weakens the effect.
2) I think I see where you are going with this one, but I think the shot would benefit from a vertical crop, excluding the left hand 50%
3) The lines created by the foliage do not add enough to the image. I would like to see a tighter crop, centered on the rock and the background wall- much stronger.
4) Cool shot. I think I'd crop in a bit from the top to remove the background trees, while leaving the framing low hanging branches.
5) My favorite. Try bringing down the brightness a bit.
6) I like this one, too. Decreasing the brightness and increasing the contrast might make it seem more abstract.
John