Hi
"Mark A. Hershberger" already discovered/guessed my still missing 2nd point:
There seem to be an (unknown?) rendering bug. See URL http://commons.wikimedia.org/wiki/File:Flag_of_Iran.svg and the flag's/file's version of 20:14, 21. Jun. 2012 .
The original sized image had no artifacts, only this thumb nail in the preview (and maybe others of these 4+4 fixed sized png-images on the description page, but I forgot which). I remeber that I deleted all leading digit 0 from coordinates in a SVG path-command inside for the center emblem. Maybe this was a reason for miss-rendering at certain sizes, but I strongly wonder that this only hurts certain final absolute sizes of a rendered image so drastically.
Achim