It changed so much because the artist worked on this for a very long time and as with most artists this one's style changed but if you're talking about the random art at the end vonboche does get a few submissions from admiring fans (i highly recommend looking him up on tumblr)
The comic was started by the artist mitarashi then finished by vonboche. The bottom-right of the closing page says "a comic started by mitarashi, seamlessly completed by vonbache". "seamlessly"