I think your expecting miracles if you think an 030/50 ecs can pull off playing mpegs and/or playing modern avi files. You migt perhaps get away with postage stamp size avi and files created in the 90s (such as those that appear on the os39 cd).
Their was a scenedemo called dreamscape by Triumph which was essentially an mpeg player+anim. Maybe check it out to see what your setup can do.
