Well I have made this pic of the clothes that I found in the "picture" folder! My theory is this:
The arrow is the direction of the changing when you press the F6 button. If your villager has already the last green dress, you can't change it. I had this situation once!

(I'm not sure to be clear, I hope so

)
And I suppose it's the same for male's clothes but I didn't check it.
edit: sorry, my pic is very small! I hope you can see it!
