If there was no animation in the original mng, then why
bother with the mng format? Why not change to png, update the source code reference and be done?
Who knows?? I say we just use the .png. I suspect somebody generated the .mng from the .png to begin with as a 'place-holder' for future animation. The, for whatever reason, never followed through with the full implementation. Either that, or the place-holder was just there for individual distros to patch with their animated files. I know suse/opensuse had a couple of different icons for the start menu that they would patch into kde3 back in the 10.x days.
Unless I read objections I will replace the MNG with a PNG and update the one source code reference accordingly.
Darrell