the last one is really nice and the vignietting suits there. but in the second one not only is vignietting disturbing but also the leaf. You need to decide whether vignietting is useful here and might improve the photo or not...
"Vignetting" is that darker circular part in your frames which seems to make us look through a hole. I am not too fond of it in any of your photos here, least of all in those where it is so very strong like in Photos 6 and 8.
It works for the last one, though.
I quite like the blue background that the road surface in shadow gives you in Photo 2, but if I were you, I'd lose the vignette.