Metaru:
Don't try to generalise it like that. Most shmups don't have a light source straight from above. I guess you're reffering to a rotation problem, which most of the time isn't a problem. You've seen one sprite from his proposed game and you make all kind of assumtions.

do you know why the lightsource is often placed above SHMUP sprites?

I think it's a good idea. I can picture this in a shmup. Do some more experimenting with the idea and you'll probably get something you're really satisfied with.

Metaru: The light source is clearly coming from the infinite upper left, not just the upper left of the image.

Agreed with metaru... also, you might want to avoid dithering on space ships :S

the shading is as poor as the ship's concept. considering that is a top down point of view, you have placed the ligthsource at the top rigth corner of the imafe, wich means that the ligth source will be at the same heigh as the object, wich is quite hard to believe considering that, if this thing is suposed to be fliying around in an atmosphera or in space, the only light source posible would be a sun or similar. and, unless you're planing to draw dinamic shadows on it(=9999frames per sprite), explosions can't be considered as a lightsource.

for me, its just a cross with some random beveled shapes over it. not even close to be or look like a spacecraft, unless in a christian based universe.