I think the idea was not so much as to show off the custom girl graphics, but more in line with that you are not limited to using the default girl graphics and are free to experiment. Although you are right, those white outlines are rather distracting.
I don't think such a drastic move is needed. I mean, sure the white lines are ugliness, but the point of this screen, and others, is to say, "Hey, you can add stuff to this game! HOW AWESOME IS THAT!?" Or something to that effect.
I say this in the hopes that people will see Masako, download her, and that may lead to more downloads for Matsumori Days. Yes, I'm terrible like this.
That's a good idea. I think I'll do that. (and if a custom content creator supplies their own screenshot in the custom content page, I'll use that screenshot)