I feel it would be remiss of me not to mention the humble TempleOS support for mixing code and sprites. I can't say I've ever used the system myself, but its DolDoc format [0] offered some pretty nifty features for directly interspersing sprites into source code viewable together as one. You can see some screenshots on the hackmag page [1] under the section that reads: "If that’s not enough to impress you, open any game file and behold the unthinkable: the sprites are embedded right in the code!"

0) https://tinkeros.github.io/WbTempleOS/Doc/DolDocOverview.htm... 1) https://hackmag.com/security/templeos