I rather like the idea of being able to change some of the coloring on our pets. I don't believe they need any extra armor though.
http://gw.gamewikis.org/wiki/Animal_companion
EDIT: Animal armor is generally called barding I do believe. It could have its place if it were more of a clothing item like the holiday items. I think if anything like this were ever to be implimented it should only be the ability to dye your pet however. It would be pretty easy to impliment since they are temporarily dyed for PvP matches. How to do such a thing, use a dye on the charm animal skill, that easy. I could /sign that idea, not a pet armor or clothing though. I mean don't you guys think that dog sweaters and cat dresses look super silly?