Well...
Download:
https://pastebin.com/eu4t5EWT
Screenshot:
Spoiler: show
tileRandomizer.register(98, {68, 70, 71})
First argument is the source ID, second is a list of possible transformations. There's, by default, a 1/5 chance that the block gets transformed at all. You can edit the file directly to
-change the chance
-change the seed
Seed, you ask? Oh yeah. This library uses a standalone instance of rng.lua to ensure your level doesn't magically look different on repeat playthroughs. The seed can be any number, so feel free to experiment until you find something that suits your level.