Oh, I did something similar on my website! https://interruptkey.com
beautiful site!
The other day I realized that holding down the Option key in the System 7 Desktop Patterns control panel changes the button text from "Set Desktop Pattern" to "Set Utilities Pattern". Does anyone here happen to know what that means?
edit: holy crap, I just figured it out: "Set Utilities Pattern" replaces the background pattern of every desk accessory, such as the Calculator and Scrapbook apps, Find File, Key Caps, Puzzle— with the pattern you chose. What a different time that was!
woah that's a new one for me too! great find
(and I also did the hack of reading raw images to get the binary pattern :-D the source for the converter is also in this repo)
Demo here: https://jherrm.github.io/classic-mac-desktop-pattern/
Source: https://github.com/jherrm/classic-mac-desktop-pattern