Is there a way to change the reference point when loading an external image?

I am building a site with action script 2, have a main page which links to .swf files for photo galleries. In the .swf files I am referencing external images but my problem is such.

I have made a new symbol, a movie clip container and placed it in the top left corner of the frame in which the images are loading. I want all of the images to be placed centered in the frame, some are horizontal and some are vertical. all of the horizontal images are the same width but some are different heights. All of the vertical images are the same height but again not all the same width. What is happenning now is they are all loading to that top left reference point but this doesn’t look good. Is there any way to have the horizontal images reference the middle left of each image and then put the container in the middle left of the frame, and have another container for the verticals that is placed in the top middle of the frame? I am really stuck here and can’t find any information on this.

On thought I had was to make a transparent canvas in photoshop the size of the frame and place the images manually but then I have to either save as png and the image size skyrockets, or save as a gif and the image quality suffers…

I would really appreciate any suggestions!! Thanks for your time