Know any sites with Japanese game cover art or ad scans?

[Kitsune Sniper]

I'm looking for a bunch of sites that have Japanese game cover art, or ad / handbill / flyer ads, particularly from the NES/GB/SNES era. I'm working on a new layout for my site and figured I'd add some blog header images. So far I've got three for a few of the games I've translated, but my Google searches don't turn up as much stuff as I'd like.

Does anyone know any sites where I could find these? Just... don't mention GameFAQs, most of the stuff uploaded there is very low quality.