I assume he's referring to the massive commercial success of Holy-C and TempleOS.
(It's the only programming language with inline graphics I can think of, at least, your average esoteric visual language tend to not mix with normal code.)
You can use images inline in Racket. Decidedly less esoteric :)
I was going to mention holyC here, but I don't think it is the same thing. holyC lets you embed images etc in the code, but those images don't become part of the logic. This paper is talking about mixing graphical programming languages with textual ones (like a file with both scratch blocks and c code in)