In case of a sokoban level generated with generative ai, it is code. It is literally a set of instructions.
There is a stronger argument for png files being code and you know it, so stop pretending otherwise.
For the less technically inclined, this is what a Sokoban level looks like:
#####
#@$.#
#####
Note how it’s literally just plain data. There are graphical Sokoban implementations that replace these text characters with graphics, but there are also text-based Sokoban implementation which use exactly these characters to represent the game. On a spectrum from code and data, this at the absolute far end of non-code data. If this plain data is code, then logically all plain data must be code, which makes the distinction of code and not-code meaningless in a game.
A png file, on the other hand, uses data compression. A compressed data file basically consists of a set of instructions for reconstructing the uncompressed data. On a spectrum from code to data, this is still comfortably on the data end of the spectrum, but not quite at the extreme end.