The maker behind Grimm Knife Company does some funky stuff cast in acrylic resin.
Animal skull in resin:
Human tooth in resin:
Others:
But as mentioned, might be easier to buy a block from somebody specializing in resin and sending to your knifemaker of choice. I really like this one from @derangeddonkey on Instagram:
There's a lot of people making these on Instagram, they all seem to follow each other so it's easy to find more of them.
2nd Butch's work. I have one of his swirly green micarta handles and depending on what colors he used, it can definitely be made 'trippy'. Plus, his knives are awesome.
not to discourage the Op from his quest, but DAMN, that misc kind of resins and plasti-combos are just hell to work with (when making them) from a health standpoint. Sure does open up creative possibilities though. Good luck.