Maybe you're missing something out here Al.
You can't move the image itself. You can only inflict buttons and movieclips with as. The image will always be glued to the upper left corner since you load it dynamicly. I don't know though why you get stucked on that because if you just move the MC in the same way, as a described before, then it will look just like the image is centered on the stage, right?
It should be no problem.