The problem with this game in terms of time has always been the fact that he commissions art from a number of different artists. One does the pencils, another the inking, and another the coloring. All before finally getting back to him for assembly into the project.
All CZ himself does is the writing and coding. However, as he does commission art in an assembly line process like this, he is at the whims of the artists he hires, who usually have their own deadlines and backlogs to deal with. And hence very very slow.
So yeah he has been adding/modifying previous artwork, just usually while waiting on the main art to get shuttled through the process. You can often watch the process as several of his artists have streams. F-ing (inker) is probably the most often active on live streams, but others have been up and about.
