The way Ao Usagi did this is interesting, actually... The artist created a tag 分割霊夢; and it'll formulate the entire image. I didn't know this at first and used the bookmarks listing instead. Same result, though.
As amusing and clever as this is, part of me can't help but secretly sort of hope some other artist starts using the tag to hijack a layer and starts turning it into a different character or something, like some sort of crazy touhou sliding puzzle and/or rubix cube. (Alternatively, I'd love to see a separate project of that nature sprout from this where each artist takes a square and makes a big image.)
I don't know if I should congratulation Mysterio006 for posting something like this, or question his sanity for actually posting it. I mean was it really necessary?