This octopus stamping is popular indeed. It can be found both as a supply and in finished pieces all over etsy and the internet as a whole, and in every imaginable finish.
It is an octopus. I had to give it a try myself.
I purchased a set of two octopus stampings from jlyndesigns (and a third non-octopus stamping which has not been turned into a finished necklace yet). She included a suprise pair of starfish stampings as well, so of course I had to integrate those. Pearls were also a necessity, and lots and lots of antique brass.
The first I made has its tentacles twisted into one brass chain, dripping with pearls. The starfish creates asymmetrical detail. The necklace is long, to hang low on a wearer.
In the second, I shortened the necklace and doubled the chain. Both close with a brass toggle clasp.
Now I just have to figure out which one is mine, and then decide what to do with the other one.