[Andrés]

The ship portrait is placed transpatenly over the star background in a similar to how mini pics are always used to make it look it's in the middle of space.

A background or if the whole ship does not completely fit inside the picture will ruin that effect.

A not defined border that blends into the star background may be more acceptable.

It's your choice if you want to keep a background that makes ships look crudely cropped in those situations that are not so common anyway.