This probably should go to the gallery, but I'm not quite sure how the system there works (and how much space we've got for this forum). If I'm wrong here, please close this thread.
So I'll post extra illustrations that come with the manga in this thread bit by bit - as I can find time to scan them. The extra illustrations on the backside of the cover only come with first print editions and I don't have first print editions for every volume. So I'm sorry if they are sometimes missing.
Volumes are in no particular order.