I can’t add much, but based on the sources links I left when I created the picture dump thread I’ve been able to determine where I got this picture from.
It was first mentioned in this post by @linkdu83 , for which I will also quote the relevant part regarding the image you’ve mentioned here:
Maybe someone can translate this page to see if it holds any relevant information regarding this Pichu (although I doubt it will, based on the page and pictures in general. It’s probably a coincidental example image without saying anything about it in question, but hopefully someone who can read Japanese will counter my assumptions 
):
It’s not much, but perhaps it helps somewhat.
Keep in mind that all the sample prints shown in the first section of the main post with pictures are close to one-of-a-kind, and mostly never released to the public.
Greetz,
Quuador