Algorithms you'd want to do something like this would be dithering and quantization, just incase anyone is interested!
Shameful (-less?) plug: I’ve implemented dithering for creating bead patterns from images in my web application Beadifier https://www.beadifier.com
Neat. Would be nice if there were some examples of what a beads rendition looks like. Maybe it's obvious for people in the game. I assume they are hexagonal?
Cool! My kids are making Pikmin with perler beads right now. Maybe I'll transcribe their creations.