#1 is very good and interesting, but I've had comments that it looks too much like a zipper. A more literal spine picture might help. I would also like to see this in colour. (but thank you for listening to my first request for B&W!)
The double curved lines in #2 and #3 are good, I would again like to see some colour combinations.
#6 the dots/spine reminds me too much or a worm, or a sperm.
#4 I put out because I don't like how the circle and curved lines worked together, it seemed to either not fit, or to look like an abstract human form, but accidentally.
Incidentally an abstract human form would be interesting to see, as no one has attempted that yet.