Eric Kozlowsky left Retro Studios some time ago but the artist has confirmed he did work on the studio’s upcoming game before he left that he stated he is proud of. He noted that it may not end up in the final product but we can hope it does.
See his tweet below
I certainly hope so! I did some stuff that I'm really proud of. But games are a fluid beast, a lot could've changed since I left
— Eric Kozlowsky (@vonkoz) September 21, 2016