So yeah, I do approve of having Chopper on the cover... given the limited number of volumes, Usopp has been put off until Collection 5 for cover art. However, I think it's kind of sad that since Volume 5 will probably be episodes 104-130, which ends the Alabasta arc, we probably will never have Vivi on a cover. She's not a permanent Straw Hat, but she is definitely an honorary member. I was hoping she'd get her own cover. But of course, that would mean Usopp would have to get put off until Colection 6.