It is from a light novel instead of a manga. The first season covered the first three light novels and the intro of the 6th one, and the 4th one is a filler my guess is that we need to wait for the 7th or 8th light novel for a second season.
I have also found this.
It explains how the author of No game No life was caught tracing. Some of the tracing is only a hand or one body part, but some of them are so bad that it is the entire picture. From what I have read and seen, it seems to be the special/ poster made pictures. Even so, this makes me believe that the chances for a season 2 have decreased greatly.