When I was growing up it was a lot harder to find ambient music, but I still have barely found anything similar to the music of Creatures in instrumentation or composition.
The only thing I've found with strong similarity is As Clouds Dance by Byron Metcalf which is a very nice ambient piece with a sound similar to the Norn Terrarium and other C3 music.
Some of the music by Voyage futur gives me creatures vibes and April skulls by Pilotredsun (released under his Pilotredsky account) and the first song on Aerowave by Felipe Azvevedo make me think of the creatures one intro music, the later sounds a lot like it while the former it's just vibes.
creatures caves is your #1 resource for the creatures artificial life game series: creatures, creatures 2, creatures 3, docking station, and the upcoming creatures family.