A better illustrated explanation of these issues can be found in this thread:
* Any pixels on the outside edge of a gaseous graphic get stretched a long way. Doesn't matter with current graphics since the edges are generally transparent, but seem to be a sign that somethings wrong.
* Apparently the image is either mirrored vertically or horizontally, but never not mirrored and never mirrored both ways. We'd get a more natural, irregular effect if each graphic had more than these two positions, especially if 90° rotation was also sometimes thrown into the mix.
* And most importantly to me, the scaling range is too extreme. Sometimes the graphic can be shrunk so small that the star's halo pretty much covers it. This is what got me to investigate, since sometimes big gaps are visible in thin spiral arms. At max zoom the minimum size of a 256x256px gaseous graphic should be about 100%, i.e. 256x256px on screen. If the artist wants blank spots, he can throw some blank files in, but i don't think they look quite right.