Vector files

I am sure this is a very basic question…

I have a lot (and I mean a LOT) of library items which I am pulling in via actionscript. I am literally going to be using them to place on top of another movieclip (thing Mr.Potato head) and I was just wondering what base class I should extend my library items from?

Currently they are MovieClips, but I imagine that is not the most efficient method. I’d like to be able to change the scale of the movieclips, but everything else will be set.

Cheers guys