Wow, these look almost official!
On pixiv there are a lot of work that look so close to the original anime, manga, etc that they could be passed off as official! They call this "野生の公式" or Yasei no Koushiki. These fan arts pay attention to the thickness of lines and how the original work was colored... it really does seem like the official artists did it! Don't get them confused with the real thing, these are fan arts! Check them out.