|Ian McCaig's Sea Witch as more creature than human.|
In Hans Christian Andersen's story she is human enough to have pets, and to name certain things, so I think she would have an interest in the objects that human corpses and shipwrecks would provide her with and she'd want to collect them, but she wouldn't have a chest of drawers and a dressing table with brushes and mirrors laid out properly like in the Disney film, everything would be cluttered and in really strange places. She would have piles of things, some recognisable and some not, that would fill most of her living space except where she would sleep and work. Here's a little research into hoarding:
After a little research into octopuses I found that they rarely have skeletons, which allows them to squeeze into tiny crevices in rocks to hide from predators. Seeing as my Sea witch is half-human, she would have a skeletal structure, even if it was largely just her upper body. Also, being human, she would want and need more space for her treasures, so her home may look like it's somewhere unused, like a shipwreck or a pile of rocks from outside, but inside it would be much grander. While researching I also came across the coconut/veined octopus (Amphioctopus marginatus). It's been caught bipedal walking and gathering and using coconut shells, seashells and other debris for shelter and defense. Though they generally bury themselves in sand they use the shells to protect them as they travel. Here's a pretty cool video of it below:
Above are some images of octopuses where they create really interesting shapes, whether it's in their symmetry or ink-like curling.
Due to there being little description of the interior of the Sea Witch's home, I'm going to apply a lot of artistic licence to create something that's grand and sinister, while still feeling like it's cluttered with junk. So, onwards I go! :D