I think I may like #6 on the top row. Helmets can be difficult to design.... did you look at any real helmets? If you want to go with #6 on the top row I would be fine with that
6 was my favorite of the female characters as well, but I think I'm more interested in designing a male character since I don't have as much practice with them. If I try designing more helmets, do you think the male character would be a stronger design?
See, it's hard to know when the helmets are no in the context of the character. the helmet is one of the biggest factor is determining this character's silhouette, so I can't really say which one works best. Try pushing them to be more dramatic!