I've tried to use Nebula's white background and it works on the first song. But when I run the next song, the background lasts only a moment and finally disappears into a blank background. Afterwards, I tried to change to other backgrounds again but it still won't reappear.
Halve it to 4096x2048 and it should be fine.If not drop it again to 2048x1024.fergtm's skysphere program should do it, or even MS paint would do a good enough job.