This is a hard question! I think I could be persuaded to like most anything presented the right way. Personally, in a quilt for me, I would not like black in certain situations, batiks, somber/muted colors, a panel, cartoon characters and I'm picky about what florals I like--hard to explain. I'm on the fence about batiks--I LOVE how they are used in some quilts, but I don't see them as very useful to me yet, because of my skill level!
I really like some Amy Butler stuff, but what I have doesn't seem to be very retro. But come to think of it--I don't want to use these pieces in a quilt. I like them in smaller projects, bags, etc...