Any kind of non-human figure or non-biped is inclined to get my attention. In particular prehistoric or fantasy creatures, posable plants, insects (fantasy or real), and robots of any sort (toon, heavy sci-fi, whatever). Articulated or animated surreal versions of every day objects are also always welcome and not very common in the Poserverse.

"How would you do the Blob?"

there's a good marginalized poser critter, I think I've only ever seen a few Poser blobs or space amoebae. Probably not a big market for such things overall but sure to appeal to certain niche users (like myself).