I imported a very large gif file into a .dmi for use as an opening movie in Vengeance 56. The gif itself is about 10MB in size. Anyway, when I set the dmi as the icon for a given object, DM reports 822096128 errors. If I set the icon var to something else (i.e. no existing references to the dmi movie), no errors are reported. Despite the errors, I'm able to run the game, and it seems to run just fine.
If necessary, I could make a demo later.
edit: I forgot to mention that it cut the movie off at 98 frames (out of about 350 total). It has dimensions of 320X256.