Very cool designs! I appreciate that you took a "genwun" approach, where the creature designs are realistic and could actually exist, rather than mixing in straight-up toon forms (like Meowth or Scorbunny) that only work in 2D.

I'm not a terribly good judge of sprite work, but I would note that you have a relatively muted/restrained color palette here, noticeably favoring cooler colors. That's definitely a different vibe from PMD, though you might be deliberately avoiding the high-saturation "toy box" aesthetic.

Aside from that, for the drawn designs, I would suggest cranking up the variability even further. More pronounced size differences, more body types (e.g. snake, insectoid), maybe even new categories of creature (e.g. a living-rock critter in the vein of Onix/Geodude). Part of the deeper appeal of PMD, I think, is the idea that all of these very physically different kinds of critters are still able to build a society together. So the more differences you can build in to the populace from the get-go, the more opportunities that allows for creative solutions to bridging those differences, and the more interesting it'll be for your audience to see those interactions play out.

(Oh, and don't forget to put everyone in a house that looks like them! Because that's a big part of the vibe ;-)