Hi hi!
There are two major things I'd like to suggest and one not so major.
The first major: Adding the ability to select other walk, sit, run and idle animations from a set. While I love the current animations, I think it would be nice to allow us to pick animation sets or individual animations to help bring diversity to our creations.
Second major: Personalities. By that I mean, you mentioned you want to eventually have our creations interact with one another. I think it would be nice to do something simple to pick a personality and thus a certain way the creature would interact with another. You could take inspiration from Animal Crossing for this too!
Not so major: I think it would be nice to add hair and other tufts of fur/hair in other places. Also the ability to multi-color items would be nice but I recognize there may be limitations with the system this is constructed in on that front.
Otherwise this is super cute and I am looking forward to it being on Steam!